1.	Barium and magnesium are both in Group 2 of the Periodic Table.  Several bottles on the Group 2 shelf of the chemicals store had damaged labels.
(a)	Two bottles are clearly labelled ‘sulphate’.  The solid in bottle A dissolves easily in water but none of the solid in bottle B appears to dissolve when added to water.
Which of these two bottles contains barium sulphate?...............................................
(1)
 
(b)	Bottle C, labelled ‘magnesium carbonate’, contains a white powder.  When heated this powder produces a colourless gas that turns limewater cloudy.
State whether this label is correct and explain your answer.
................................................................................................................................
................................................................................................................................
................................................................................................................................
(2)
 
(c)	Describe a test to show that the solid in bottle D is barium hydroxide and not magnesium hydroxide.
................................................................................................................................
................................................................................................................................
................................................................................................................................
(3)
 
(d)	Bottle E is clearly labelled ‘magnesium nitrate’.  When a sample of the chemical is heated it gives off a brown gas and a gas that relights a glowing splint.
	Give the name of each of the gases formed and write an equation for this chemical reaction.
................................................................................................................................
................................................................................................................................
................................................................................................................................
................................................................................................................................
(4)
(Total 10 marks)

2.	When gaseous ammonia, NH3, is passed into dilute sulphuric acid it reacts to form a solution of ammonium sulphate, (NH4)2SO4, which may then be crystallised.
(a)	Write the equation for the neutralisation of sulphuric acid by ammonia.
................................................................................................................................
(1)
 
(b)	2.50 dm3 of impure ammonia gas was passed into excess sulphuric acid. 6.23 g of crystals of ammonium sulphate were produced.
(i)	Calculate the amount (in moles) of ammonium sulphate in 6.23 g of ammonium sulphate (Mr = 132).

(1)
 
(ii)	Calculate the amount (in moles) of ammonia required to produce this mass of ammonium sulphate.

(1)
 
(iii)	What is the number of moles of pure ammonia in the 2.50 dm3 sample of impure ammonia?

(1)

(iv)	Calculate the percentage purity of the ammonia used in this experiment. (Molar volume of a gas at the temperature and pressure of the experiment 24.0 dm3.)

(2)
 
(v)	Calculate the volume of 1.30 mol dm–3 sulphuric acid needed to make 6.23 g of ammonium sulphate.

(2)
(Total 8 marks)

3.	(a)	When the Group 2 element calcium is added to water, calcium hydroxide and hydrogen are produced.
Write an equation for the reaction.
................................................................................................................................
(1)
(b)	State the trend in solubility of the hydroxides of the Group 2 elements as the atomic mass of the metal increases.
................................................................................................................................
(1)
 
(c)	(i)	Define the term first ionisation energy, and write an equation to represent the change occurring when the first ionisation energy of calcium is measured.
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
(4)
 
(ii)	State and explain the trend in the first ionisation energy of the Group 2 elements.
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
(3)
(Total 9 marks)

4.	(a)	The compounds lithium chloride, sodium bromide and potassium iodide can be distinguished from one another by the use of flame tests.
(i)	Complete the following table.
Compound	Flame colour	
Lithium chloride		
Sodium bromide		
Potassium iodide		

(3)
(ii)	Explain the origin of the colours in flame tests.
......................................................................................................................
......................................................................................................................
(2)

(b)	These compounds can also be distinguished from one another by the use of concentrated sulphuric acid.
(i)	State what would be seen when concentrated sulphuric acid is added to separate solid samples of each of these compounds.
Lithium chloride...............................................................................................
......................................................................................................................
Sodium bromide...............................................................................................
......................................................................................................................
Potassium iodide..............................................................................................
(4)
(ii)	Write an equation, including the state symbols, for the reaction between solid lithium chloride and concentrated sulphuric acid.
......................................................................................................................
(2)
(Total 11 marks)

5.	(a)	Seawater contains aqueous bromide ions. During the manufacture of bromine, seawater is treated with chlorine gas and the following reaction occurs:
		2Br– + Cl2 ® Br2 + 2Cl–
(i)	Explain the term oxidation in terms of electron transfer.
......................................................................................................................
......................................................................................................................
(1)
 
(ii)	Explain the term oxidising agent in terms of electron transfer.
......................................................................................................................
......................................................................................................................
(1)

(iii)	State which of the elements chlorine or bromine is the stronger oxidising agent and explain the importance of this in the extraction of bromine from seawater, as represented in the equation above.
......................................................................................................................
......................................................................................................................
......................................................................................................................
(2)
 
(b)	When sodium chlorate(I), NaClO, is heated, sodium chlorate(V) and sodium chloride are formed.
(i)	Write the ionic equation for this reaction.
......................................................................................................................
(2)
(ii)	What type of reaction is this?
......................................................................................................................
(1)
 
(c)	During one process for the manufacture of iodine the following reaction occurs:
		2IO3 + 5SO2 + 4H2O ® I2 + 8H+ + 5SO
(i)	Deduce the oxidation number of sulphur in:
SO2................................................................................................................
SO.............................................................................................................
(2)
 
(ii)	Use your answers to part (c)(i) to explain whether SO2 has been oxidised or reduced in the above reaction.
......................................................................................................................
......................................................................................................................
(1)

(iii)	Name a reagent that could be used to confirm that a solution contains iodine, and state what would be seen.
......................................................................................................................
......................................................................................................................
(2)
(Total 12 marks)

6.	A student carried out an experiment to find the percentage of calcium carbonate, CaCO3, in a sample of limestone following his own plan. The student’s account of the experiment, results and calculation of the mean titre are given below.

(a)	The accuracy of the student’s method was judged to be poor by his teacher. The  teacher suggested that the procedure in II could be improved and that the titres  used to calculate the mean were incorrectly chosen.
(i)	Suggest, with a reason, one improvement to the student’s procedure in II.
Improvement.................................................................................................
.....................................................................................................................
Reason..........................................................................................................
.....................................................................................................................
(2)
 
(ii)	Recalculate a value of the mean making clear which titres you choose and giving your answer to an appropriate number of significant figures.

(2)
 
(b)	(i)	Using your answer to (a)(ii), calculate the amount (number of moles) of sodium hydroxide in the mean titre.

(1)
 
(ii)	Hence state the amount (number of moles) of hydrochloric acid in a 25.0 cm3 portion of the acidic solution transferred in IV.

(1)

(iii)	Hence calculate the amount (number of moles) of hydrochloric acid remaining after the reaction in II.

(1)
 
(iv)	Calculate the number of moles of hydrochloric acid transferred to the beaker in II.

(1)
 
(v)	Hence calculate the amount (number of moles) of hydrochloric acid used in the reaction in II.

(1)
 
(vi)	Hence calculate the amount (number of moles) of calcium carbonate and the mass of calcium carbonate in the sample of limestone,
{Mr (CaCO3) = 100}.

(2)

(vii)	Hence calculate the percentage of calcium carbonate by mass in the sample of limestone.

(1)
 
(c)	The burette used in the titrations had an uncertainty for each reading of ±0.05 cm3.
(i)	Which of the following should be regarded as the actual value of the titre in titration 3?
Circle the letter corresponding to your chosen answer.
	A   between 14.80 cm3 and 14.90 cm3
	B   between 14.825 cm3 and 14.875 cm3
	C   between 14.75 cm3 and 14.95 cm3
(1)
 
(ii)	Suggest one reason why a student may obtain volumes outside the uncertainty of the burette when carrying out a titration.
.......................................................................................................................
.......................................................................................................................
(1)
(Total 14 marks)

7.	(a)	Sodium reacts with cold water.
(i)	What would you see as the reaction proceeds?
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)

(ii)	Write the balanced chemical equation for this reaction.
..........................................................................................................................
(2)
 
(b)	Calculate the volume of gas produced if 3.0 g of sodium reacts with an excess of water.
	(One mole of any gas at the temperature and pressure of the experiment occupies
24 dm3.)

(3)
(Total 7 marks)

8.	(a)	Hydrogen chloride can be made from sodium chloride and concentrated sulphuric acid. Write a balanced chemical equation to represent this reaction.
....................................................................................................................................
(1)
 
(b)	(i)	How would you confirm that a solution said to be HCl(aq) contained chloride ions?
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(3)
 
(ii)	Hydrogen chloride is soluble in water. Explain why the solution is acidic.
..........................................................................................................................
..........................................................................................................................
(2)
 
(c)	(i)	Give a chemical test for chlorine, stating what you would do and what you would see.
..........................................................................................................................
..........................................................................................................................
(2)
 
(ii)	Hydrogen chloride can be oxidised to chlorine by lead(IV) oxide, PbO2. Write the oxidation numbers of lead and of chlorine in the boxes provided.

(2)
 
(d)	Sodium iodide reacts with concentrated sulphuric acid to give iodine, not hydrogen iodide. Explain why iodides react differently from chlorides in this case.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 12 marks)

9.	(a)	(i)	State how a flame test would distinguish between samples of calcium nitrate, Ca(NO3)2 and barium nitrate, Ba(NO3)2.
..........................................................................................................................
..........................................................................................................................
(2)

(ii)	Explain the origin of the flame colour.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
 
(3)
(b)	Write the equation for the action of heat on barium nitrate.
....................................................................................................................................
(2)
 
(c)	(i)	What is meant by the term polarising power as applied to cations?
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
 
(ii)	Give two factors which affect the polarising power of cations.
..........................................................................................................................
..........................................................................................................................
(2)

(iii)	Use this information to explain why it is easier to decompose magnesium nitrate than barium nitrate by heating.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(3)
(Total 14 marks)

10.	(a)	Complete the following table:
Element	State at room temperature	
Chlorine	Gas	
Bromine		
Iodine		
(2)
 
(b)	Describe how you could use solutions of silver nitrate and ammonia to distinguish a solution of sodium iodide from a solution of sodium bromide.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(4)
(Total 6 marks)

11.	(a)	Complete and balance the following equations:
(i)	Ca + O2 ® .....................................................................................................
(1)
(ii)	Na2O + H2O ® ...............................................................................................
(1)
(iii)	Na2O + HCl ® ...............................................................................................
(2)
 
(b)	State and explain the trend in thermal stability of the carbonates of the Group 2 elements as the group is descended.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(3)
(Total 7 marks)

12.	(a)	Describe how to use the technique of volumetric analysis to determine the concentration of aqueous sodium hydroxide given a burette containing 0.100 mol dm–3 sulphuric acid.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(5)

(b)	25 cm3 of an aqueous solution of sodium hydroxide, concentration 0.100 mol dm–3 was titrated with 0.100 mol dm–3 sulphuric acid.
(i)	Write the equation for the complete reaction of sodium hydroxide and sulphuric acid.
............................................................................................................................
(1)
 
(ii)	Calculate the volume of the 0.100 mol dm–3 sulphuric acid needed to exactly neutralise 25.0 cm3 of 0.100 mol dm–3 aqueous sodium hydroxide.

(2)
 
(c)	A careless student used a conical flask to store the alkali and did not wash it clean before use in the titration. Assuming that ‘emptying’ the conical flask actually left 0.20 cm3 of alkali adhering to the inside of the flask.
	Calculate the percentage error in the titration result.

(2)
(Total 10 marks)

13.	(a)	State the number of protons, neutrons and electrons in a  ion.
	protons: ……………… 	neutrons: ………………	electrons: ………………
(3)
 
(b)	The mass spectrum of lithium shows two peaks. Their mass/charge ratios and percentage abundance are shown below.
Mass/charge	% Abundance	
6.02	7.39	
7.02	92.61	
 
	Calculate the relative atomic mass of lithium, giving your answer to three significant figures.

(2)
 
(c)	Describe a test that you would do to distinguish between solid lithium chloride and solid sodium chloride. Clearly state what you would do and what you would see with both substances.
………….…………………………………………………………………………….
………….…………………………………………………………………………….
………….…………………………………………………………………………….
………….…………………………………………………………………………….
(3)
(Total 8.marks)

14.	(a)	Bromine is a p-block element Define the term p-block element.
………….…………………………………………………………………………..
………….…………………………………………………………………………..
(1)
 
(b)	(i)	Give the colour and physical state of bromine at room temperature,
Colour ………………………	Physical state ……………..…………….
(2)
 
(ii)	State what you would see when aqueous bromine is added to a solution of potassium iodide.
………….……………….……………………………………………………..
………….……………….……………………………………………………..
(1)
 
(c)	Aqueous bromine will oxidise Fe2+ ions to Fe3+ ions.
(i)	Write the ionic half-equation for the reduction of bromine to bromide ions.
………….……………….……………………………………………………..
(1)
 
(ii)	Write the ionic half-equation for the oxidation of Fe2+ ions to Fe3+ ions.
………….……………….……………………………………………………..
(1)
 
(iii)	Hence write the overall ionic equation for the reaction of Fe2+ ions with bromine.
………….……………….……………………………………………………..
(1)

(d)	Chlorine and bromine react with aqueous sodium hydroxide in a similar way at room temperature.
(i)	Write the equation for the reaction of bromine with aqueous sodium hydroxide.
………….……………….……………………………………………………..
(2)
 
(ii)	What type of reaction is this?
………….……………….……………………………………………………..
(1)
 
(e)	Potassium bromide, KBr, reacts with potassium bromate, KBrO3, in the presence of dilute sulphuric acid to form bromine, potassium sulphate and water.
5KBr + KBrO3 + 3H2SO4 ® 3Br2 + 3K2SO4 + 3H2O
 
(i)	Give the oxidation numbers of bromine in
KBr …………………..   KBrO3 ………………....   Br2 .....…………………
(3)
 
(ii)	Which substance in this reaction is the oxidising agent? Give a reason for your choice.
Substance: …………………………………………………………………….
Reason: ………………………………………………………………………..
………….……………….……………………………………………………..
(2)
(Total 15 marks)

15.	Two important nitrogen compounds are ammonium nitrate and nitrogen(I) oxide.
	These substances can be prepared as shown by the following reactions.
Reaction A	NH3(aq) + HNO3(aq)    NH4NO3(aq)
Reaction B	NH4NO3(s)    N2O(g) + 2H2O(g)
 
(a)	Name the types of reaction illustrated by equations A and B.
A .................................................................................................................................
B .................................................................................................................................
(2)
 
(b)	Reaction A was carried out by titration.
	10.0 cm3 of 1.00 mol dm–3 ammonia solution was reacted with nitric acid of concentration 0.500 mol dm–3.
(i)	What piece of apparatus would you use to measure out the 10.0 cm3 of ammonia solution?
............................................................................................................................
(1)
(ii)	What piece of apparatus would you use to add the nitric acid?
............................................................................................................................
(1)
 
(iii)	Suggest a suitable indicator you could use to find the endpoint of this titration and give the colour change you would expect.
Indicator ............................................................................................................
	Colour change
from ....................................................... to .......................................................
(2)
 
(iv)	What volume of nitric acid would be required to react exactly with the 10.0 cm3 of the ammonia solution?

(1)

(v)	This experiment was repeated without the indicator. Describe how you would obtain dry crystals of ammonium nitrate from the resulting solution.
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
(3)
 
(c)	In reaction B, 4.0 g of solid ammonium nitrate reacted.
(i)	What is the mass of 1 mole of ammonium nitrate, NH4NO3?
	Use the Periodic Table as a source of data.

(1)
 
(ii)	How many moles of nitrogen(I) oxide, N2O, were formed when 4.0 g of ammonium nitrate reacted?

(1)

(iii)	What volume (at room temperature and pressure) will this amount of nitrogen(I) oxide occupy?
[Molar volume is 24 dm3 mol–1 at room temperature and pressure.]

(1)
(Total 13 marks)

16.	The following table was used to record the results of experiments in which aqueous solutions of halogen elements were added to aqueous solutions of potassium halides.

(a)	(i)	The ticked box indicates that a reaction occurred when bromine solution was added to potassium iodide solution.
	Place ticks in appropriate empty boxes to indicate the other experiments in which you would expect reactions to have occurred.
(1)
(ii)	Give ONE observation you would expect to make when bromine solution is added to potassium iodide solution.
............................................................................................................................
(1)

(iii)	Write a balanced ionic equation for the reaction in (ii).
(Omit or delete any spectator ions).

(1)
 
(iv)	Select ONE of the products of the reaction in (ii).
	Describe a test you could carry out to confirm its identity, indicating the result of the test.
Product ...............................................................................................................
Test .....................................................................................................................
............................................................................................................................
Result..................................................................................................................
............................................................................................................................
(2)
 
(b)	Iodine and its compounds are quite expensive and it is sometimes worthwhile recovering this element from solutions containing iodide ions. This can be done by adding a solution of potassium dichromate acidified with sulphuric acid. Iodine is then precipitated and can be separated from the mixture.
	An unbalanced ionic equation for the reaction is:
Cr2O72– (aq) + H+ (aq) + I– (aq)   ®   2Cr3+ (aq) + I2 (s) + H2O (l)
 
(i)	Identify the two elements which show a change of oxidation number during the reaction, giving their initial and final oxidation numbers.
	First element.......................................
	Initial oxidation number..............      Final oxidation number ..............................
	Second element ..................................
	Initial oxidation number..............      Final oxidation number ...............................
(3)
 
(ii)	Using oxidation numbers (or otherwise), balance the equation:
Cr2O72– + ........H+  + ........I–  ®  2Cr3+ + ........I2 + ........H2O
(1)
 
(c)	The halogen elements have a wide variety of commercial and industrial uses.
	Bromine, for example, is extracted from sea water and used to make compounds such as bromomethane, CH3Br, an insecticide.
(i)	Why must strict precautions be taken if it is necessary to transport bromine from the extraction plant to another manufacturing site?
............................................................................................................................
............................................................................................................................
(1)
 
(ii)	Suggest ONE environmental concern arising from the use of gaseous bromomethane to destroy insects in a grain store.
............................................................................................................................
............................................................................................................................
(1)
(Total 11 marks)

17.	(a)	Calcium and magnesium react vigorously with dilute hydrochloric acid but with dilute sulphuric acid the calcium stops reacting even though the magnesium continues.
(i)	Write a balanced equation for the reaction between magnesium metal and dilute hydrochloric acid. Include all state symbols.
......................................................................................................................
(2)
 
(ii)	Calcium reacts slightly more vigorously than magnesium with dilute hydrochloric acid. Suggest, in terms of atomic structure, why this is so.
......................................................................................................................
......................................................................................................................
......................................................................................................................
(2)
 
(iii)	Suggest why calcium stops reacting with dilute sulphuric acid after a few seconds even though it did react initially.
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
(2)
 
(b)	(i)	Write balanced chemical equations for the thermal decomposition of potassium nitrate and calcium nitrate. Do not include state symbols.
Potassium nitrate
......................................................................................................................
(1)
Calcium nitrate
......................................................................................................................
(2)
 
(ii)	State the relative thermal stability of potassium nitrate and calcium nitrate and explain how it is related to the sizes and charges of the ions involved.
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
(5)
(Total 14 marks)

18.	A 1.62 g sample of impure sodium carbonate was dissolved in distilled water and then made up to 250 cm3. 25.0 cm3 of this solution was put into a conical flask and three drops of methyl orange indicator added. This was titrated against a 0.105 mol dm–3 solution of hydrochloric acid until the end point was reached. The titration was repeated three more times. The results are shown below.
	1	2	3	4	
Burette reading (final)	25.30	25.30	25.85	25.95	
Burette reading (at start)	0.00	0.50	0.75	1.25	
Titre/cm3	25.30	24.80	25.10	24.70	
 
	The equation for the reaction is:
Na2CO3  +  2HCl  ®  2NaCl  +  H2O  +  CO2
 
(a)	(i)	The student was supplied with a burette that may not have been clean. What precautions should be taken before filling it with the standard hydrochloric acid solution?
......................................................................................................................
......................................................................................................................
......................................................................................................................
(2)
 
(ii)	Describe the colour change that tells when the end point has been reached.
......................................................................................................................
......................................................................................................................
(2)
 
(b)	(i)	Select the appropriate titres and calculate their mean.
......................................................................................................................
......................................................................................................................
(2)

(ii)	Calculate the amount (in moles) of hydrochloric acid solution in the mean titre.

(1)
 
(iii)	Calculate the amount (in moles) of pure sodium carbonate in 25.0 cm3 of solution.

(1)
 
(iv)	Calculate the amount (in moles) of pure sodium carbonate in 250 cm3 of solution.

(1)
 
(v)	Calculate the mass of pure sodium carbonate, Na2CO3, taken.

(2)

(vi)	Calculate the percentage purity of the sample of sodium carbonate.

(1)
(Total 12 marks)

19.	(a)	(i)	Strontium hydroxide, Sr(OH)2, is one of the products formed when strontium reacts with water.
	Write a balanced equation for the reaction of strontium with water.

(2)
 
(ii)	Explain why strontium is described as being oxidised in this reaction.
..........................................................................................................................
..........................................................................................................................
(1)
 
(b)	An experiment was carried out to measure the solubility of strontium hydroxide.
Solid strontium hydroxide was added to water until a layer of solid remained on the base of the container. The mixture was then left overnight. 25.0 cm3 portions of strontium hydroxide solution were then measured by pipette and titrated with a
0.100 mol dm–3 solution of nitric acid. 16.9 cm3 of the nitric acid was needed to react with the strontium hydroxide in the solution.
	The equation for the reaction is
Sr(OH)2(aq)  +  2HNO3(aq)  ®  Sr(NO3)2(aq)  +  2H2O(l)

(i)	Why was the mixture left overnight before carrying out the titration?
..........................................................................................................................
(1)
 
(ii)	Calculate the number of moles of nitric acid used in the titration.

(1)
 
(iii)	Calculate the number of moles of strontium hydroxide in 1 dm3 of the solution.

(2)
 
(iv)	Calculate the solubility of strontium hydroxide in g dm–3.
Use the Periodic Table as a source of data.

(2)

(c)	(i)	Crystals of hydrated strontium nitrate have the formula Sr(NO3)2.4H2O.
	How would you make a dry sample of hydrated strontium nitrate crystals from a solution of pure strontium nitrate?
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
 (3)
 
(ii)	Hydrated strontium nitrate crystals decompose when heated.
Complete and balance the equation for the reaction.
2Sr(NO3)2.4H2O(s) → ..........H2O(l) + .......... SrO(s) + .......... NO2 (g) + ................
(2)
 
(iii)	A 0.5 mol dm–3 solution of strontium nitrate was mixed with a 0.5 mol dm–3 solution of potassium sulphate, K2SO4.
	Write an equation for the reaction which occurs. Add state symbols to the equation, using the data below.
		Solubility
	mol/1000 g water
	KNO3	3.75
SrSO4	7.11 × 10–4

(2)
(Total 16 marks)

20.	(a)	A 2.20 g sample of potassium nitrate, KNO3, was dissolved in water to produce 50.0 cm3 of potassium nitrate solution.
	Calculate the concentration of this solution in mol dm–3.

(2)
 
(b)	A 2.20 g sample of potassium nitrate was heated strongly and the following reaction occurred.
2KNO3(s) ® 2KNO2(s) + O2(g)
(i)	Calculate the mass of potassium nitrite, KNO2, produced.

(2)

(ii)	Calculate the volume of oxygen gas produced.
	(One mole of gas occupies a volume of 24.0 dm3 under the conditions of the experiment).

 
(2)
(c)	State and explain the trend in the thermal stability of the nitrates of Group I as the atomic number increases.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(3)

(d)	An analysis of a potassium compound gave the following results.
Element	Percentage by mass	
potassium	56.5%	
carbon	8.7%	
oxygen	34.8%	
	Deduce the empirical formula of this compound.

(3)
(Total 12 marks)

21.	(a)	Define the term oxidising agent in terms of electron transfer, and suggest which element in Group 7 is the strongest oxidising agent.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(2)

(b)	Chlorine can react with hydroxide ions to produce chloride ions, chlorate(l) ions and water.
(i)	Write the ionic equation for this reaction. There is no need to include state symbols.
.....................................................................................................................................
(2)
(ii)	What type of reaction is taking place in (b)(i)?
.....................................................................................................................................
(1)
 
(c)	(i)	Write an equation for the reaction between concentrated sulphuric acid and solid sodium chloride.
.....................................................................................................................................
(1)
(ii)	State ONE observation that you would make.
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(d)	Draw the shapes of the following molecules, and mark on the diagram the value of the bond angles in each case.
(i)	BCl3

(2)

(ii)	PCl5

(3)
(Total 12 marks)

22.	A laboratory technician is given the task of making up 5 dm3 of aqueous sodium hydroxide of concentration 0.100 mol dm–3. The technician finds the following data on sodium hydroxide.
Formula NaOH	
Soluble in water	
Solid which absorbs moisture and acidic gases from the air	
Solid is corrosive	
Reacts with acids in aqueous solution
e.g. 2NaOH(aq)  +  H2SO4(aq)  ®  Na2SO4(aq)  +  2H2O(i)	
	The technician prepares the solution and checks its concentration, following the procedure outlined below.
I	The technician calculates the mass of sodium hydroxide needed to make 5 dm3 of 0.100 mol dm–3 solution.
11	The technician adds 5 dm3 of water to a plastic bucket.
III	The technician weighs the calculated mass of sodium hydroxide, transfers it to the plastic bucket and stirs until the sodium hydroxide has dissolved.
IV	The technician titrates 25.0 cm3 samples of the sodium hydroxide solution with 0.0500 mol dm–3 sulphuric acid.
V	The mean titre is 23.50 cm3 of 0.0500 mol dm–3 sulphuric acid.
 
(a)	Calculate the mass of sodium hydroxide that the technician needs to take, to make 5 dm3 of solution of concentration 0.100 mol dm–3.

(2)

(b)	Calculate the concentration, in mol dm3, of the sodium hydroxide solution from the titration results in IV and V.

(3)
 
(c)	The actual concentration of the sodium hydroxide solution is not exactly 0.100 mol dm–3 as the technician intended.
(i)	Suggest ONE reason for this, which is a consequence of the way in which the technician makes up the solution.
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(ii)	Suggest ONE reason for this, which is a consequence of the chemical properties of the sodium hydroxide.
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(d)	(i)	Explain the meaning of the term corrosive as applied to solid sodium hydroxide.
.....................................................................................................................................
.....................................................................................................................................
(1)

(ii)	Suggest a safety precaution that the technician should take (apart from wearing a laboratory coat and eye protection) when weighing out the sodium hydroxide.
.....................................................................................................................................
(1)
(Total 9 marks)

23.	(a)	Draw a ‘dot-and-cross’ diagram for a magnesium ion.
	Show ALL the electrons present and give the charge on this ion.

(2)
 
(b)	Why do salts containing magnesium ions give no colour in a flame test?
....................................................................................................................................
....................................................................................................................................
(1)
(Total 3 marks)

24.	This question is about a mixture, M, which contains 80% of potassium bromide, KBr, 
and 20% of potassium chloride, KCl, by mass.
(a)	When concentrated sulphuric acid was added to mixture M and the mixture gently warmed, four different gases were given off.
(i)	What would happen to moist universal indicator paper when held in this mixture of gases?
..........................................................................................................................
..........................................................................................................................
(1)
 
(ii)	What would you see if a glass rod, dipped into concentrated ammonia solution, was held in these gases?
..........................................................................................................................
..........................................................................................................................
(1)
(iii)	Which of these gases would be responsible for turning potassium dichromate(VI) solution from orange to green?
..........................................................................................................................
(1)
 
(b)	(i)	What would you see when silver nitrate solution is added to a solution of mixture M?
..........................................................................................................................
..........................................................................................................................
(1)
(ii)	After adding silver nitrate solution to a solution of mixture M in (b)(i), concentrated ammonia solution is added.
	What would you see? Justify your answer.
..........................................................................................................................
..........................................................................................................................
(2)

(c)	The graph below shows how the solubilities of potassium bromide and potassium chloride vary with temperature.

(i)	What is meant by a saturated solution?
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)

(ii)	125 g of mixture M, containing 80% KBr and 20% KCl by mass, was added to 100 g of boiling water to make a solution.
	Calculate the masses of KBr and KCl present in mixture M.

	Use your calculation and the graph to predict which crystals will form on cooling to 20 °C, and what will be left in the solution.
..........................................................................................................................
..........................................................................................................................
(3)
(Total 11 marks)

25.	(a)	(i)	Write the ionic half-equation to show the oxidation of calcium, Ca, to calcium ions, Ca2+.
.....................................................................................................................................
(1)
 
(ii)	Write the ionic half-equation to show the reduction of water to hydrogen, H2, and hydroxide ions, OH–.
.....................................................................................................................................
(1)
 
(iii)	Combine the two ionic half-equations above to produce an equation which shows the effect of adding calcium to water.
.....................................................................................................................................
(1)
 
(iv)	State what you would expect to see when calcium is added to water.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
 
(b)	State the trend in solubility of the hydroxides of the Group 2 elements as the atomic number increases.
.....................................................................................................................................
(1)
 
(c)	Write an equation to show the reaction between sodium and chlorine, to produce sodium chloride.
.....................................................................................................................................
(2)
(Total 8 marks)

26.	(a)	Identify a halogen which, at room temperature, is:
a solid ....................................................................................................................................
a liquid ..................................................................................................................................
a gas ......................................................................................................................................
(3)
 
(b)	Explain why the hydrogen halides, such as hydrogen chloride, HCl, are:
(i)	water soluble
.....................................................................................................................................
.....................................................................................................................................
(2)
(ii)	acidic in aqueous solution ....................................................................................................................................
....................................................................................................................................
(1)

(c)	By consideration of intermolecular forces, explain why the boiling temperature of hydrogen fluoride, HF, is higher than that of hydrogen iodide, HI.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(2)
 
(d)	Deduce the oxidation number of chlorine in the following:
ClO– ..................................................................................................................................
ClO3– ..................................................................................................................................
(2)
(Total 10 marks)

27.	You are provided with the following apparatus and materials.
·	A burette ready to use filled with a solution of aqueous sodium hydroxide.
·	An aqueous solution of 0.0500 mol dm–3 ethanedioic acid.
·	Phenolphthalein indicator.
·	Access to the full range of laboratory volumetric apparatus.

(a)	Describe how you would carry out titrations to find the volume of sodium hydroxide that reacts with 25.0 cm3 of the aqueous ethanedioic acid.
	In your answer you must include how you would detect the end point and what you would do to obtain a reliable result.
	You do not need to include any details of calculations you may carry out on your results.
............................................................................................................................................
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............................................................................................................................................
............................................................................................................................................
(6)
 
(b)	The reaction involved in the titration is
(COOH)2(aq) + 2NaOH(aq) ® (COONa)2(aq) + 2H2O(l)
	25.0 cm3 of the aqueous 0.0500 mol dm–3 ethanedioic acid required 25.50 cm3 of the aqueous sodium hydroxide for neutralisation.

(i)	Calculate the amount (moles) of ethanedioic acid in 25.0 cm3 of the solution.

(1)
 
(ii)	Calculate the amount (moles) of sodium hydroxide in 25.50 cm3 of the solution.

(1)
 
(iii)	Calculate the concentration of the sodium hydroxide solution in mol dm–3.

(1)

(c)	Calculate the mass of hydrated ethanedioic acid, (COOH)2.2H2O, needed to make up 200 cm3 of aqueous 0.0500 mol dm–3 solution. Give your answer to three significant figures.

(3)
 
(d)	When making up the solution of ethanedioic acid a student, by mistake, uses a 200 cm3 instead of a 250 cm3 volumetric flask. The student dissolves the mass of ethanedioic acid crystals calculated to make up 250 cm3.
	Explain what effect this would have on the student's volume of sodium hydroxide solution used in the titration.
[No calculation is required in your answer.]
............................................................................................................................................
............................................................................................................................................
............................................................................................................................................
............................................................................................................................................
............................................................................................................................................
(2)
(Total 14 marks)

28.	The foot and mouth virus affects farm animals such as cattle and sheep. One of the recommended disinfectants used to try to prevent foot and mouth disease from spreading is sodium carbonate solution.
(a)	The sodium carbonate solution is used to disinfect footwear because it is alkaline and the virus cannot survive if exposed to a pH greater than 9.
	Suggest ONE reason why the disinfectant may not destroy all of the virus present on footwear.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(b)	One method that could be used to determine the concentration of a solution of sodium carbonate is to titrate it with hydrochloric acid of known concentration.
	A 25.0 cm3 sample of sodium carbonate solution was titrated using 1.00 mol dm–3 hydrochloric acid to determine its concentration. 42.0 cm3 of acid was needed to neutralise the sodium carbonate solution. The indicator used to find the end-point was methyl orange.
(i)	Write a balanced equation for the reaction between a solution of sodium carbonate and hydrochloric acid, including appropriate state symbols.

(2)
 
(ii)	What piece of apparatus should you use to add the hydrochloric acid?
............................................................................................................................
(1)
 
(iii)	State the colour of the indicator:
in sodium carbonate solution ............................................................................
at the end-point of the titration. ........................................................................
(2)

(c)	(i)	Calculate the number of moles of hydrochloric acid added to the sodium carbonate solution.

(1)
(ii)	Use your answer from (c)(i) and your equation from (b)(i) to work out the number of moles of sodium carbonate in the 25.0 cm3 sample.

(1)
 
(iii)	Use your answer from (c)(ii)	to work out the concentration, in mol dm–3, of the sodium carbonate solution.

(1)
(Total 9 marks)

29.	In the manufacture of beer, brewers often add small amounts of salts of Group 2 elements to the water used. These salts influence the chemical reactions during the brewing process.
Two such salts are calcium sulphate and magnesium sulphate.
(a)	A flame test can be used to confirm that a sample of a salt contains calcium ions.
(i)	Describe how you would carry out a flame test.
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
(3)
 
(ii)	A positive test results in a brick-red flame colour. Describe the changes that occur in calcium ions to produce a colour.
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
(2)
 
(iii)	Impurities in the salt may lead to other colours being observed in the flame.
What metal ion is likely to be present if a yellow flame is seen?
............................................................................................................................
(1)
 
(b)	Magnesium sulphate can be used in its anhydrous form, MgSO4(s), or in its hydrated form, MgSO4.7H2O(s).
	An experiment was carried out to find the enthalpy change when hydrated magnesium sulphate dissolved completely in water.
MgSO4.7H2O(s)    MgSO4(aq)  +  7H2O(l)
	12.3 g of hydrated magnesium sulphate was added to 100 g of water in a simple calorimeter and the temperature was found to fall by 1.1 °C.
 
(i)	Calculate the energy change, in joules, that occurred in the experiment, using the relationship
Energy change (J) = 4.18 × mass of water × temperature change

(2)

(ii)	Calculate the number of moles of hydrated magnesium sulphate used in the experiment. Use the Periodic Table as a source of data.

(2)
 
(iii)	Use your answers to (i) and (ii) to calculate the enthalpy change for the reaction.
Include a sign and units in your final answer, which should be given to 2 significant figures.

(2)
 
(c)	The enthalpy change as hydrated magnesium sulphate is converted to anhydrous magnesium sulphate is very difficult to measure. The Hess Cycle below can be used to find this enthalpy change, ΔHr.

(i)	Use the cycle to write an expression for ΔHr using ΔH1 and ΔH2.

(1)

(ii)	Use your expression in (c)(i) and your answer from (b)(iii) to calculate ΔHr.
	Include a sign and units in your final answer, which should be given to 2 significant figures.

(2)
(Total 15 marks)

30.	(a)	(i)	Describe how you would make up exactly 250 cm3 of aqueous sodium carbonate, of accurately known concentration, from solid anhydrous sodium carbonate, Na2CO3.
	You may assume that you are given a weighing bottle containing an appropriate amount of sodium carbonate, but that you still need to find the mass of sodium carbonate by weighing.
	You do not need to include details of calculating the concentration in your answer.
.....................................................................................................................................
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.....................................................................................................................................
(6)

(ii)	Calculate the concentration, in mol dm–3, of a solution containing 1.28 g of anhydrous sodium carbonate, Na2CO3, in 250 cm3 of solution.

(3)
 
(b)	In a series of titrations, hydrochloric acid was added, from a burette, to 25.0 cm3 portions of the sodium carbonate solution pipetted into conical flasks. Methyl orange was added as the indicator.
	The burette readings are shown in the table below.
	1	2	3	
Burette reading at end/cm3	24.80	48.90	24.40	
Burette reading at start/cm3	0.00	24.80	0.00	
Titre/cm3	24.80	24.10	24.40	
	Number of titrations used to calculate the mean (average) titre: 1, 2 and 3
Mean titre = 24.43 cm3 of hydrochloric acid
(i)	Give the colour change that would be observed at the end point.
From ..................................................... to ..........................................................
(1)

(ii)	The student carrying out the titrations was criticised by the teacher for not carrying out at least one more titration.
Suggest a reason why the teacher’s criticism was justified.
................................................................................................................................
................................................................................................................................
................................................................................................................................
(1)
 
(c)	Using the mean titre given and your answer to (a)(ii), calculate the concentration of the hydrochloric acid in mol dm–3. The equation for the reaction in the titration is:
Na2CO3(aq) + 2HCl(aq) ® 2NaCl(aq) + CO2(g) + H2O(l)

(2)

(d)	Before titration 2, the student rinsed the pipette with water and then immediately used it to transfer sodium carbonate solution to the conical flask for the titration.
	If 0.5 cm3 of water was present in the pipette, calculate the percentage error this would cause in the volume of hydrochloric acid needed in this titration.

(1)
(Total 14 marks)

31.	1-bromobutane can be prepared by the reaction of hydrogen bromide with butan-l-ol.
C4H9OH + HBr ® C4H9Br + H2O
	Sodium bromide and sulphuric acid are used to generate the hydrogen bromide in the reaction flask.
	The stages in the preparation are listed below.
·	Mix sodium bromide, 50% sulphuric acid and butan-1-ol, then heat the mixture under reflux for about 30 minutes.
·	Rearrange the apparatus for distillation and distil off the impure 1-bromobutane.
·	Transfer the impure 1-bromobutane to a separating funnel so that the 1-bromobutane may be separated from the aqueous layer and then washed.
·	Add anhydrous calcium chloride to the 1-bromobutane and leave to stand. When the liquid becomes clear, filter off the calcium chloride.
·	Carry out a final distillation to obtain pure 1-bromobutane.
Information on 1-bromobutane, C4H9Br
Density 1.3 g cm–3
Boiling temperature 102 °C
Harmful by skin absorption
Immiscible with water.	
 
(a)	(i)	Calculate the maximum mass of 1-bromobutane that may be prepared from 4.0 g of butan-1-ol if all the other reagents are in excess.
[Molar masses: butan-l-ol = 74 g mol–1, 1-bromobutane = 137 g mol–1.]

(1)

(ii)	In a preparation, 5.9 g of 1-bromobutane is obtained from 4.0 9 of butan-1-ol. Calculate the percentage yield.

(1)
 
(b)	The diagrams below show the reflux apparatus and the separating funnel used in the preparation.

(i)	Explain the purpose of the vertical condenser in the reflux apparatus.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)

(ii)	On the diagram of the separating funnel, draw and label two layers to show
1-bromobutane and water during the washing stage.
(1)
 
(iii)	What is the purpose of adding anhydrous calcium chloride to the 1-bromobutane?
................................................................................................................................
(1)
 
(iv)	Draw a labelled diagram of the distillation apparatus that is used to obtain pure 1-bromobutane.

(4)
 
(c)	Give ONE safety precaution (apart from wearing eye protection and a laboratory coat) that should be taken during the preparation. Give a reason for your choice.
.......................................................................................................................................
.......................................................................................................................................
(1)
(Total 11 marks)

32.	Name a metal, in Group 1 or 2, which has compounds that do not give a colour to the flame in a flame test.
................................................................................................................................................
(Total 1 marks)

33.	This question is about strontium and some of its compounds.
(a)	Complete the electronic configuration of the strontium atom, using s,p,d notation.
	Use the Periodic Table as a source of data.
1s22s2 .............................................................................................................................
(2)
 
(b)	(i)	Write a balanced equation which represents the change that corresponds to the first ionisation energy of a strontium atom. Include state symbols in the equation.

(2)

(ii)	The first ionisation energy of strontium is marked on the grid below. Estimate and plot the next THREE ionisation energies for strontium.

(2)
 
(c)	Suggest why strontium compounds are used in distress flares and fireworks.
......................................................................................................................................
......................................................................................................................................
(1)
 
(d)	Give the formula of
(i)	the strontium ion in strontium compounds .......................................................
(1)
(ii)	strontium hydroxide. .........................................................................................
(1)

(e)	Write balanced equations for the following reactions, including state symbols.
(i)	Strontium with water to produce strontium hydroxide and a gaseous product.

(2)
(ii)	Solid strontium hydroxide with dilute hydrochloric acid.

(2)
 
(f)	Estimate the pH of a saturated aqueous solution of strontium hydroxide.
......................................................................................................................................
(1)
(Total 14 marks)

34.	(a)	Complete the following table.
Element	Physical state at room
temperature	Colour	
chlorine			
bromine			
iodine			
(3)
 
(b)	(i)	Write the equation for the reaction between concentrated sulphuric acid and solid potassium chloride, KCl.
............................................................................................................................
(1)

(ii)	When potassium bromide, KBr, reacts with concentrated sulphuric acid, bromine and sulphur dioxide are produced.
	Give the oxidation numbers of bromine and sulphur in the reactants and products. Hence identify the oxidising agent, giving a reason for your choice.
	KBr .................	H2SO4 .................
	Br2 .................	SO2 .................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
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(4)
(Total 8 marks)

35.	(a)	Complete the electronic configuration for calcium, Ca.
1s2 .................................................................................................................................
(1)
 
(b)	(i)	Define the term first ionisation energy.
............................................................................................................................
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(3)

(ii)	Explain why the first ionisation energy of calcium is lower than that of magnesium.
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(3)
 
(c)	A sample of magnesium contains three isotopes of mass numbers 24, 25 and 26.
(i)	In terms of sub-atomic particles, state ONE similarity and ONE difference between these isotopes.
Similarity ...........................................................................................................
............................................................................................................................
Difference ..........................................................................................................
............................................................................................................................
(2)

(ii)	The following data were obtained from the mass spectrum of this sample of magnesium.
Peak at m/e	%
24.0	78.6
25.0	10.1
26.0	11.3
	Calculate the relative atomic mass of this sample of magnesium. Give your answer to 3 significant figures.

(2)
(Total 11 marks)

36.	Sodium and chlorine react together in a redox reaction to form sodium chloride, NaCl.
(i)	Write the half equation for
	the oxidation of sodium, Na
.....................................................................................................................................
	the reduction of chlorine, Cl2.
.....................................................................................................................................
(2)
 
(ii)	Write the equation for the reaction of sodium with chlorine.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 3 marks)

37.	(a)	(i)	Potassium superoxide contains 54.9 % potassium by mass.
Show that the empirical formula of this compound is KO2.

(3)
 
(ii)	Give the oxidation number of oxygen in the compound KO2.
............................................................................................................................
(1)

(b)	Which of potassium nitrate or lithium nitrate has the higher thermal stability?
Explain your answer.
......................................................................................................................................
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(3)
(Total 7 marks)

38.	A student investigated the ease with which Group 2 metal carbonates thermally decompose when heated with a Bunsen burner.
XCO3(s) → XO(s) + CO2(g)
	The student heated each carbonate separately in a test tube. The volume of gas collected in a gas syringe was measured after two minutes.

(a)	Each test tube must be heated directly by a Bunsen flame in an identical manner.
Suggest how this can best be achieved.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(2)
 
(b)	In each experiment, the student used the same number of moles of metal carbonate.
	The mass of magnesium carbonate, MgCO3, heated was 0.21 g.
	Calculate the mass of barium carbonate, BaCO3, that should be used for a valid comparison.

(3)
 
(c)	(i)	Calculate the maximum volume of carbon dioxide that would be produced by the complete decomposition of 0.21 g of magnesium carbonate.
	[1 mol of gas occupies 24 000 cm3 under the conditions of the experiment.]

(2)
 
(ii)	The balance used to weigh the magnesium carbonate is accurate to ± 0.01 g.
Calculate the percentage error in the mass of the magnesium carbonate weighed.

(1)
 
(d)	The following results were obtained after heating each sample for two minutes.
Metal carbonate in the
test tube	Volume of gas produced
/cm3	
None	9	
MgCO3	20	
CaCO3	13	
SrCO3	11	
BaCO3	9	
 
(i)	Why was a test tube containing no metal carbonate heated?
............................................................................................................................
............................................................................................................................
............................................................................................................................
(1)
 
(ii)	Describe a chemical test that would be used to confirm the identity of the gas produced.
Test ....................................................................................................................
Result .................................................................................................................
(2)

(iii)	Use the results in the table to describe the trend in thermal stability of the Group 2 metal carbonates.
............................................................................................................................
............................................................................................................................
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(2)
(Total 13 marks)

39.	(a)	Describe TWO observations which can be made when crystals of hydrated magnesium nitrate are heated.
Observation 1 ................................................................................................................
.......................................................................................................................................
Observation 2 ................................................................................................................
.......................................................................................................................................
(2)
 
(b)	Name ONE of the gases evolved. Describe a test for this gas to confirm its identity and give the result.
Name of gas ..................................................................................................................
Test and result ...............................................................................................................
.......................................................................................................................................
(2)
(Total 4 marks)

40.	(a)	Barium carbonate can be converted into barium chloride solution by a reaction with hydrochloric acid. In a particular experiment, an excess of barium carbonate was added to 25 cm3 of hydrochloric acid of concentration 1.0 mol dm–3.
(i)	Describe how you would obtain dry crystals of hydrated barium chloride, BaCl2.2H2O, from the reaction mixture.
................................................................................................................................
................................................................................................................................
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................................................................................................................................
................................................................................................................................
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(4)
 
(ii)	Write a balanced equation, including state symbols, for this reaction.

(2)
 
(iii)	Calculate the number of moles of hydrochloric acid used in the experiment.

(1)
 
(iv)	Calculate the mass of one mole of hydrated barium chloride, BaCl2.2H2O. Use the Periodic Table as a source of data.

(1)

(v)	Calculate the theoretical mass of crystals which could be obtained.

(1)
 
(vi)	Suggest a reason why this mass of crystals is unlikely to be obtained in practice.
................................................................................................................................
................................................................................................................................
................................................................................................................................
(1)
 
(b)	(i)	What colour do barium compounds produce in a flame test?
................................................................................................................................
(1)
(ii)	When carrying out a flame test on a solid, state a suitable material on which it can be supported in the flame.
................................................................................................................................
(1)
(Total 12 marks)

41.	(a)	A few crystals of potassium iodide were put into a test tube with a similar quantity of phosphoric acid, H3PO4. The mixture was warmed. Misty white fumes were seen at the mouth of the test tube.
(i)	Give the name or formula of the misty white fumes which formed in this reaction.
................................................................................................................................
(1)
 
(ii)	Write a balanced equation for the reaction. State symbols are not required.
H3PO4 +         KI →	+
(2)
 
(iii)	A sample of the misty white fumes was collected and dissolved in water.
	What reagent would be used to confirm the identity of the halide ion present in the solution? State what you would expect to see when it is used.
Reagent ..................................................................................................................
Observation ............................................................................................................
(2)
 
(b)	If potassium iodide crystals are reacted with concentrated sulphuric acid, a complicated reaction occurs in which a mixture of gases is produced.
(i)	What would you see, other than misty white fumes, when this reaction occurs? Give ONE observation.
................................................................................................................................
................................................................................................................................
(1)
 
(ii)	One of the gases in the mixture is hydrogen sulphide, H2S. It can be identified by holding a piece of filter paper soaked in a solution of lead nitrate, Pb(NO3)2, or lead ethanoate, (CH3CO2)2Pb, in the gas.
	What would be observed if hydrogen sulphide is present?
................................................................................................................................
................................................................................................................................
(1)
 
(iii)	Suggest the name of the lead compound which forms in this reaction, using Stock notation.
........................................................................
(1)

(iv)	The equation below shows how hydrogen sulphide could be produced from sulphuric acid in a redox reaction.
	9H2SO4 + 8KI → H2S + 8KHSO4 + 4H2O + 4I2
	Which element is oxidised in the reaction and which is reduced? Justify your answer by calculating oxidation numbers.
	Element oxidised .................................
	Initial oxidation number .......................  Final oxidation number ......................

	Element reduced ..................................
	Initial oxidation number .......................  Final oxidation number ......................
(3)
 
(c)	An experiment was carried out to measure the purity of a sample of potassium iodide.
	1.75 g of impure potassium iodide was dissolved in water, and excess chlorine was passed through the solution. The following reaction occurred.
Cl2(g) + 2KI(aq) → I2(aq) + 2KCl(aq)
	The solution was warmed to drive off the excess chlorine and was then made up to 250 cm3 in a volumetric flask. A titration was used to measure the concentration of iodine in the solution.
(i)	What solution could be used in a titration to measure the concentration of iodine?
................................................................................................................................
(1)
 
(ii)	Name a suitable indicator and state the colour change at the end-point of this titration.
	Indicator .................................................................................................................
	Colour change from ......................................     to ...............................................
(2)

(iii)	A titration showed that the solution contained 4.8 × 10–4 moles of iodine, I2, in a 25 cm3 sample. Calculate the number of moles of potassium iodide, KI, which were in the original impure sample.

(1)
 
(iv)	Calculate the percentage purity of the potassium iodide.
Use the Periodic Table as a source of data.

(2)
(Total 17 marks)

42.	(a)	Calcium reacts with water to produce calcium hydroxide and hydrogen.
	Write the equation for this reaction. Give TWO observations that could be made during this reaction.
Equation
.....................................................................................................................................
Observations
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
 
(b)	State the trend in the solubility of the Group 2 hydroxides, as the atomic mass of the Group 2 element increases.
.....................................................................................................................................
(1)
 
(c)	(i)	Show that the following data are consistent with the empirical formula CaN2O6.
Symbol of element	% by mass	
Ca	24.4	
N	17.1	
O	58.5	

(2)
 
(ii)	Explain why the thermal stability of the Group 2 nitrates increases as the atomic number of the Group 2 element increases.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 10 marks)

43.	(a)	Define the term oxidising agent in terms of electron transfer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(b)	(i)	Suggest which halogen is the strongest oxidising agent.
...........................................................................
(1)
 
(ii)	What is the physical state of bromine at room temperature?
...........................................................................
(1)
 
(c)	State the appearance of a gas evolved when concentrated sulphuric acid is added to solid sodium bromide.
.....................................................................................................................................
(1)
 
(d)	Give the oxidation number of chlorine in each of the following species.
ClO– ......................................................................
ClO3– ......................................................................
(2)

(e)	Chlorine reacts with sodium hydroxide.
	Write an ionic equation for this reaction and explain, in terms of oxidation numbers, why this is a disproportionation reaction.
	Equation
.....................................................................................................................................
	Explanation
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
 
(f)	(i)	Write an equation, including state symbols, to show the process that occurs when the first electron affinity of chlorine is measured.
...........................................................................................................................
(2)
 
(ii)	Explain why the second electron affinity of chlorine would be endothermic.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 14 marks)

44.	Magnesium oxide is a basic oxide which produces an alkaline solution with water. Write an equation to show how the oxide ion, O2–, acts as a base in the reaction with water.
...............................................................................................................................................
(Total 1 mark)

45.	This question is concerned with some redox reactions of iodine.
(a)	Iodide ions can be converted into iodine using chlorine.
In the laboratory this can be carried out by adding an aqueous solution of chlorine to one of sodium iodide.
(i)	Write an ionic equation, with state symbols, but omitting spectator ions, for the reaction which takes place.
...........................................................................................................................
(2)
 
(ii)	A hydrocarbon solvent is added to the reaction mixture, which is then shaken for a few minutes, and the layers allowed to settle. What colour is this hydrocarbon layer?
...........................................................................................................................
(1)
 
(iii)	The procedure above is repeated using an aqueous solution of sodium bromide, instead of sodium iodide. Give the colour of the hydrocarbon layer in this case.
...........................................................................................................................
(1)
 
(b)	Iodine molecules can be converted into iodide ions using sulphur dioxide. An unbalanced equation is given below.
I2(aq) + SO2(aq) + H2O(l) ® I–(aq) + SO42–(aq) + H+(aq)
(i)	Give the oxidation number of
iodine in I2	............	iodine in I–	............
sulphur in SO2	............	sulphur in SO42–	............
(2)
 
(ii)	Identify, with a reason, the reducing agent in this reaction.
...........................................................................................................................
...........................................................................................................................
(1)

(iii)	Use the information above, or any other means, to balance the equation below.
I2(aq) +	SO2(aq) +	H2O(l) ®	Ι–(aq) +	SO42–(aq) +	H+(aq)
(1)
 
(c)	The reaction between iodine and sulphur dioxide can be used to estimate the concentration of sulphur dioxide, which is used as a preservative in wines.
	In such a determination, a sample of red wine was treated with activated charcoal in order to decolorise it. After filtration to remove the activated charcoal, 25.0 cm3 portions of the decolorised wine were titrated with 0.00100 mol dm–3 aqueous iodine, using starch as the indicator. An average titre of 12.2 cm3 was obtained.
(i)	Why is there a need to decolorise the red wine before samples are titrated?
...........................................................................................................................
(1)
 
(ii)	What is the colour change at the end-point of this titration?
...........................................................................................................................
(1)

(iii)	Use the information above and the balanced equation in (b)(iii) to calculate:
·	the number of moles of iodine used in each titration

·	the number of moles of sulphur dioxide with which this iodine reacted

·	the concentration, in mol dm–3, of sulphur dioxide in the red wine.

(3)
 
(iv)	Suggest why the use of activated charcoal leads to an inaccurate estimate of the sulphur dioxide content of the wine.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 14 marks)

46.	Flame tests were performed on the following compounds of calcium and sodium.
(i)	State the flame colour in each case:
calcium hydroxide ......................................................................................................
sodium hydroxide .......................................................................................................
(2)

(ii)	Explain the origin of the colours obtained in flame tests.
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 5 marks)

47.	(a)	Sodium iodide reacts with chlorine to produce sodium chloride and iodine.
(i)	State the oxidation numbers of the iodine and chlorine species in the spaces provided.
	2NaI	+	Cl2	→	2NaCl	+	I2
	..........		..........		..........		.........
(2)
 
(ii)	Use these oxidation numbers to explain why this reaction is a redox reaction.
...........................................................................................................................
...........................................................................................................................
(2)

(iii)	Calculate the maximum mass of iodine that could be produced from 30.0 g of sodium iodide.

(3)
 
(iv)	Calculate the volume of chlorine gas required to produce this amount of iodine.
	[1 mol of gas occupies 24 dm3 under the conditions of the experiment]

(1)
 
(b)	(i)	Give the colour of iodine and its physical state at room temperature and pressure.
Colour ........................................................................................
Physical state .............................................................................
(2)

(ii)	Write an equation, including state symbols, to represent the process occurring when the first ionisation energy of iodine atoms is measured.
...........................................................................................................................
(2)
(Total 12 marks)

48.	Before a solution of hydrochloric acid can be used in volumetric analysis, its concentration must be found accurately.
(a)	Suggest why hydrochloric acid cannot be made up as an accurate (standard) solution 	from pure hydrogen chloride.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(b)	The accurate concentration of a solution of hydrochloric acid can be found by titrating it against a standard solution of sodium carbonate.
This is made by dissolving a known mass of anhydrous sodium carbonate, Na2CO3, in distilled water. Distilled water is added to make the solution up to exactly 250 cm3 in a graduated flask.
	Give ONE reason why the sodium carbonate is dissolved in distilled water and then made up to 250 cm3 of solution, rather than just dissolved in 250 cm3 of distilled water.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)

(c)	The following results were obtained for the titration of 25.0 cm3 of 0.0500 mol dm–3 sodium carbonate solution, Na2CO3, against hydrochloric acid.
Na2CO3 + 2HCl ® 2NaCl + CO2 + H2O
Number of titration	1	2	3	
Burette reading (final) / cm3	31.10	32.55	30.30	
Burette reading (initial) / cm3	0.00	2.05	0.00	
Volume of HCl used / cm3	31.10	30.50	30.30	
 
(i)	Which TWO titrations should be used to calculate the mean (average) titre?
Explain your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
 
(ii)	Calculate the mean titre.

(1)
 
(iii)	Calculate the amount (moles) of sodium carbonate, Na2CO3, in 25.0 cm3 of the 0.0500 mol dm–3 solution.

(1)
 
(iv)	Hence calculate the amount (moles) of hydrogen chloride, HCl, used.

(1)
 
(v)	Calculate the concentration of the hydrochloric acid solution to three significant figures.

(2)
(Total 9 marks)

49.	(a)	Write an equation for the reaction of calcium with oxygen to form calcium oxide, CaO.
.....................................................................................................................................
(1)

(b)	Draw a ‘dot and cross’ diagram of calcium oxide, CaO, showing all the electrons. Indicate the charges clearly on your diagram.

(2)
 
(c)	(i)	Name the compound formed when calcium oxide reacts with water.
...........................................................................................................................
(1)
 
(ii)	Which pH or pH range would include the pH of a saturated solution of the product of this reaction?
pH	0–4	5–6	7	8–9	10–14	
................................................................
(1)
(Total 5 marks)

50.	Sodium carbonate forms hydrated crystals. These contain water of crystallisation and their formula can be written as Na2CO3.xH2O.
	The value of x can be found by titrating a sodium carbonate solution, which is alkaline, with hydrochloric acid as follows:
·	7.15 g of hydrated sodium carbonate crystals were dissolved in water and made up to exactly 250 cm3.
·	10.0 cm3 of this solution was pipetted into a conical flask.
·	The solution was titrated with hydrochloric acid of concentration 0.100 mol dm–3.
·	20.0 cm3 of the hydrochloric acid was needed.
 
	The sodium carbonate in the crystals reacts as shown.
Na2CO3(aq) + 2HCl(aq) ® 2NaCl(aq) + CO2(g) + H2O(l)
 
(a)	Name a container suitable for making up exactly 250 cm3 of solution.
.....................................................................................................................................
(1)
 
(b)	Suggest a suitable indicator for the titration and state the colour change you would see at the end-point.
Indicator ......................................................................................................................
Colour change from .................................................to ...............................................
(2)

(c)	Calculate the mass of hydrated crystals present in the 10.0 cm3 sample.

(1)
 
(d)	Calculate the number of moles of hydrochloric acid used in the titration.

(1)
 
(e)	Use your answers from (c)	and (d)	to calculate the mass of the hydrated crystals which would react with two moles of hydrochloric acid.

(1)
 
(f)	Deduce the molar mass of the hydrated sodium carbonate, using your answer to (e) and the equation for the reaction.
.....................................................................................................................................
(1)
 
(g)	The molar mass of sodium carbonate, Na2CO3, is 106 g mol–1. Use this value and your answer to (f) to work out the value of x in the formula for the hydrated crystals.
	If you did not get an answer to (f) use the value 196 (this is not the answer you would get if you do the calculation correctly).
	Use the Periodic Table as a source of data.

(2)
(Total 9 marks)

51.	This question is about the chemistry of sodium and magnesium.
(a)	Sodium and chlorine react together as shown in the equation.
2Na(s) + Cl2(g) ® 2NaCl(s)
	Is sodium oxidised or reduced in this reaction? Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)

(b)	(i)	Sodium chloride and magnesium chloride can be distinguished by carrying out a flame test. State the observation you would make for each.
Sodium chloride	.........................................................................................
Magnesium chloride	.........................................................................................
(2)
 
(ii)	Explain the changes which occur when electrons in sodium produce a flame
colour.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
 
(iii)	Suggest ONE use for the coloured light produced by sodium.
...........................................................................................................................
(1)
 
(c)	Write the electron configuration of a magnesium ion, Mg2+, using s, p notation.
.....................................................................................................................................
(1)
 
(d)	The table below gives some ionisation energies for sodium and magnesium.
	First ionisation
energy /
kJ mol–1	Second ionisation
energy /
kJ mol–1	
Sodium	496	4563	
Magnesium	738		

(i)	Write the chemical equation, with state symbols, which corresponds to the first ionisation energy of magnesium.

(2)
 
(ii)	Explain why the first ionisation energy of magnesium is greater than the first ionisation energy of sodium.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
 
(iii)	Predict a value for the second ionisation energy of magnesium. Explain your choice.
Value ........................................kJ mol–1
Explanation .......................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
 
(e)	Which atom has the larger radius, sodium or magnesium? Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 15 marks)

52.	(a)	Complete and balance an equation for each of the following reactions. Do not include state symbols.
(i)	Ba +	H2O	→ ...............................................
(1)
(iii)	NaCl +	H2SO4	→ ...............................................
(1)
 
(b)	State the flame colours produced by compounds of:
(i)	barium .................................................................................
(1)
(ii)	lithium ................................................................................
(1)
 
(c)	Explain how compounds of elements in Groups 1 and 2 produce colours in the flame test.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)

(d)	When potassium is burnt in excess oxygen, a compound is produced that contains 54.9 % potassium.
	Calculate the percentage of oxygen present and hence calculate the empirical formula of this compound.

(3)
(Total 10 marks)

53.	Tartaric acid is an organic acid. Volumetric analysis can be used to find out how many acid, –COOH, groups each molecule of the acid contains.
	The formula of tartaric acid can be represented in this acid-base reaction as HxTa.
	Ta represents the rest of the tartaric acid molecule, and x is the number of hydrogen atoms in the molecule which are part of the acid, –COOH, groups.
	The equation for its reaction with sodium hydroxide can be written as follows:
	HxTa + xNaOH → NaxTa + xH2O
	The value of x can be found by experiment. 25.0 cm3 of 0.110 mol dm–3 tartaric acid solution was titrated with 0.235 mol dm–3 sodium hydroxide solution, using phenolphthalein as the indicator. The following results were obtained.
	1	2	3	
Burette reading (final) / cm3	36.25	23.50	47.35	
Burette reading (initial) / cm3	12.30	0.05	24.00	
Volume of NaOH used / cm3	23.95	23.45	23.35	
 
(a)	In this titration what is the colour change for the phenolphthalein indicator?
From ..................................................
to ........................................................
(1)
 
(b)	State why the mean (or average) titre should be based only on titrations 2 and 3.
.....................................................................................................................................
(1)
 
(c)	Calculate the mean titre.

(1)
 
(d)	(i)	Calculate the amount (moles) of tartaric acid in 25.0 cm3 of 0.110 mol dm–3 solution.

(1)
 
(ii)	Calculate the amount (moles) of sodium hydroxide in the mean titre.

(1)

(iii)	Calculate the number of moles of sodium hydroxide that reacts with 1 mol of tartaric acid.

(1)
 
(iv)	Hence state the value of x, which is also the number of –COOH groups in each tartaric acid molecule.
x = ....................
(1)
 
(e)	Tartaric acid has a molar mass of 150 g mol–1. The percentage composition by mass is C 32%, H 4%, O 64%.
	Use these data to show that the molecular formula of tartaric acid is C4H6O6.

(4)

(f)	Most burettes are capable, if read correctly, of giving a reading which is ±0.05 cm3 of the true value.
	Suggest why the experiment is designed to give a titre of between 20 to 30 cm3, rather than 5 to 10 cm3. Justify your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 13 marks)

54.	(a)	Hydrogen chloride can be prepared by reacting concentrated sulphuric acid with solid sodium chloride.
	Write an equation for the reaction which occurs. State symbols are not required.

(2)

(b)	When concentrated sulphuric acid is added to solid sodium bromide, the products of the reaction include sulphur dioxide and bromine.
	2H2SO4 + 2NaBr → Br2 + SO2 + 2H2O + Na2SO4
	Sulphur and bromine change oxidation number in this reaction.
(i)	Write the oxidation numbers at the start and the end of the reaction.
Sulphur changes from ..................... to .....................
(1)
Bromine changes from ..................... to .....................
(1)
(ii)	Explain why the numbers in the balanced equation are consistent with the changes in oxidation number.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
 
(c)	The boiling points of three hydrogen halides are shown below
Hydrogen halide	Boiling point
/K	
Hydrogen chloride	188	
Hydrogen bromide	206	
Hydrogen iodide	238	

(i)	Explain the trend in boiling point of the three hydrogen halides.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)	Predict a value for the boiling point of hydrogen fluoride. Explain your reason for choosing this value.
Predicted value ......................................
	Explanation
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 11 marks)

55.	(a)	Write the equations to show the action of heat on the following solid nitrates. State symbols are not required.
(i)	lithium nitrate, LiNO3.
...........................................................................................................................
(2)
(ii)	caesium nitrate, CsNO3.
...........................................................................................................................
(1)

(b)	The solubilities of the sulphates and hydroxides of calcium and barium are shown below. Use the information in the table to answer the questions that follow.
Substance	Solubility	Substance	Solubility	
CaSO4	slightly soluble	Ca(OH)2	slightly soluble	
BaSO4	insoluble	Ba(OH)2	soluble	
 
(i)	Both calcium and barium metals react with water to give the metal hydroxide and hydrogen gas.
	What difference would you expect to see after calcium metal and barium metal have reacted with water?
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
 
(ii)	The reaction between barium metal and excess dilute sulphuric acid stops after a very short time. Suggest an explanation for this.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)

(c)	Suggest the solubility in water of radium sulphate. Put a cross () in the correct box.
A	Very soluble		
B	Soluble		
C	Slightly soluble		
D	Insoluble		
(1)
 
(d)	Write the ionic equation for the reaction of calcium metal with dilute hydrochloric acid. Include state symbols in your equation.
.....................................................................................................................................
(2)
(Total 10 marks)

56.	A titration is carried out by adding sodium hydroxide solution from a burette to 25.0 cm3 of aqueous 0.0500 mol dm–3 butanedioic acid, (CH2COOH)2, to which a few drops of phenolphthalein have been added.
	(CH2COOH)2(aq) + 2NaOH(aq) → (CH2COONa)2(aq) + 2H2O(l)
	Diagram I

(a)	A preliminary (‘rough’) titration shows that between 23.0 cm3 and 24.0 cm3 of sodium hydroxide is required to react with the butanedioic acid solution.
	Describe the procedure you would follow, using the apparatus shown in Diagram I, for a second, accurate titration. Include in your description the colour change at the end point.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
 
(b)	The burette readings recorded by a student carrying out the titrations are shown in the table below.
Titration numbers	1	2	3	
Burette reading
(final) / cm3	23.90	23.60	23.65	
Burette reading
(initial) / cm3	0.00	0.00	0.15	
Titre/cm3	23.90	23.60	23.50	
Used in mean ()				

(i)	On Diagram II below, show the level of the sodium hydroxide solution when the final burette reading is recorded in titration 3.
	Diagram II
	
(1)
 
(ii)	Calculate the mean (or average) titre.
	Show which titres you have used in your calculation by putting a tick () in the appropriate boxes in the table above.

(2)
 
(c)	(i)	Calculate the amount (moles) of butanedioic acid, (CH2COOH)2, in 25.0 cm3 of the 0.0500 mol dm–3 solution.

(1)
 
(ii)	Calculate the amount (moles) of sodium hydroxide, NaOH, in the mean titre.

(1)
(iii)	Calculate the concentration of the sodium hydroxide solution in mol dm–3. Give your answer to three significant figures.

(1)
(Total 10 marks)

57.	Calcium nitrate decomposes on strong heating.
(a)	Balance the equation for the reaction which takes place.
	Ca(NO3)2(s) → CaO(s) + NO2(g) + O2(g)
(1)

(b)	A little water is added to the solid product of this reaction and the mixture is tested with full-range pH indicator paper.
(i)	What colour will the indicator paper turn?
...........................................................................................................................
(1)
 
(ii)	Write the formula of the ion responsible for turning the indicator paper this colour.
...........................................................................................................................
(1)
(Total 3 marks)

58.	(a)	What colour do lithium compounds produce during a flame test?
.....................................................................................................................................
(1)
(b)	In what way do the electronic transfers taking place in the production of a flame colour differ from those occurring when lithium atoms ionise?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 2 marks)

59.	(a)	Lithium chloride, potassium carbonate and sodium iodide can be distinguished using flame tests. Complete the table below.
	Formula	Flame colour	
lithium chloride	LiCl		
potassium carbonate	K2CO3		
sodium iodide	NaI		
(2)
 
(b)	Explain the origin of the colours in the flame test.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
 
(c)	Write equations for the following reactions. Do not include state symbols.
(i)	Lithium chloride and concentrated sulphuric acid.
...........................................................................................................................
(1)
 
(ii)	Sodium iodide solution and silver nitrate solution.
...........................................................................................................................
(1)
(Total 6 marks)

60.	Read the passage below straight through and then more carefully. Answer the questions that follow.
	Fluorine
	Fluorine was first isolated by the French chemist Henri Moissan in 1886 after twenty-five years of continuous research. Fluorine is the most reactive element, reacting with nearly all organic and inorganic chemicals. It started to be produced on an industrial scale in the 1940s. It was needed to make uranium(VI) fluoride, UF6, a chemical essential for the enrichment of uranium which was needed initially for the first atomic bombs and is now used in some nuclear power stations.
	Fluorine is produced industrially by the electrolysis of an electrolyte made by dissolving anhydrous potassium fluoride in anhydrous hydrogen fluoride. Anhydrous hydrogen fluoride is a poor conductor of electricity so it cannot be electrolysed on its own. A 2:1 mixture of hydrogen fluoride and potassium fluoride has high electrical conductivity and a melting point of about 70°C. An aqueous solution of hydrofluoric acid cannot be used because hydroxide ions would be preferentially discharged at the anode.
 
	The electrolysis cell uses a carbon anode and a steel cathode. The anode is made of hard carbon, not graphite, since graphite would rapidly disintegrate due to infiltration of the small fluorine atoms between the carbon layers. A typical cell has up to 40 anodes and contains 1,250 kg of electrolyte. Such a cell can work at 12 V with a current of 6,000 A producing 4 kg of fluorine per hour. Because of the hydrogen fluoride impurities, about 2.08 mol of hydrogen fluoride are needed to make each mole of fluorine, F2. Cells operate at about 90°C. Cooling is necessary to maintain this temperature. This is achieved by a cooling jacket around the cell through which water is pumped at 80°C.
	Hydrogen gas is collected from the cathode. It is contaminated with hydrogen fluoride gas which is removed by passing the mixture through sodium or potassium hydroxide solution. Fluorine gas, also contaminated with hydrogen fluoride, is collected from the anode. The hydrogen fluoride is removed by reaction with sodium fluoride to form sodium hydrogen difluoride, NaHF2. The electrolyte has to be continually replenished by the addition of hydrogen fluoride. Fluorine is used immediately or liquefied and stored. Fluorine is transported as a gas in steel containers.

	Fluorine is still used to make uranium(VI) fluoride in a two-step process. First, uranium(IV) fluoride is made from uranium(IV) oxide and hydrofluoric acid, then uranium(IV) fluoride is reacted with fluorine directly. An alternative second step is to react uranium(IV) fluoride with chlorine trifluoride (made by reacting fluorine with chlorine).
	Fluorine is also used to make sulphur hexafluoride, by direct fluorination of sulphur. The reaction is highly exothermic and is self-sustaining without the application of heat. Crude gas from the reactor is heated at 500°C to disproportionate any disulphur decafluoride present.
	S2F10(g) → SF6(g) + SF4(g)
	The mixture is then washed with sodium hydroxide to remove sulphur tetrafluoride.
	Sulphur hexafluoride is an important gaseous electrical insulator in high voltage transformers or X-ray equipment.
	Fully saturated fluorocarbons made from fluorine have many uses, including use as refrigerants, lubricants, and in artificial blood. Many anaesthetics, such as enflurane and isoflurane, are made indirectly from fluorine. Important inorganic compounds made from fluorine include nitrogen trifluoride and tungsten hexafluoride used in electronics manufacture and ‘graphite fluoride’ used in battery manufacture.
(538 words)
	(Source: adapted from Blue John and family: F, HF and Fluorides by Harold Fielding and Brian Lee, Chemistry in Britain, April 1978)
 
(a)	(i)	Suggest why the electrolytic cell needs to be cooled.
...........................................................................................................................
...........................................................................................................................
(1)
 
(ii)	Explain why water at 80°C is used to cool the cell rather than water at a lower temperature.
...........................................................................................................................
...........................................................................................................................
(1)
 
(b)	Give the oxidation numbers of:
Chlorine in chlorine trifluoride ..................
Sulphur in disulphur decafluoride ..................
(2)
 
(c)	In the production of uranium(VI) fluoride from uranium(IV) oxide, in which of the reactions is uranium oxidised?
	Justify your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
 
(d)	Suggest ONE reason for and ONE reason against the enrichment of uranium.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 7 marks)

61.	The data below shows the decomposition temperatures of the carbonates of two Group 2 elements.
Compound	Decomposition temperature / °C	
MgCO3	400	
BaCO3	1360	
	Use the idea of polarisation of ions to explain why MgCO3 decomposes more readily than BaCO3.
...............................................................................................................................................
...............................................................................................................................................
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...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 3 marks)

62.	(a)	State the flame colours of
(i)	barium
...........................................................................................................................
(1)
(ii)	strontium
...........................................................................................................................
(1)

(b)	When barium is burnt in excess oxygen a compound containing 81.1% barium and 18.9% of oxygen is formed.
	Calculate the empirical formula of this compound.

(2)
 
(c)	(i)	Write the equation for the reaction of barium with water. Do not include any state symbols.
...........................................................................................................................
(1)
 
(ii)	When a small piece of barium is added to water, the barium gets smaller and eventually disappears.
	State TWO other observations you could make.
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(2)
 
(iii)	What would be the effect of adding a piece of blue litmus paper and a piece of red litmus paper to the aqueous product of the reaction in (ii)?
Red litmus .........................................................................................................
Blue litmus ........................................................................................................
(1)
(Total 8 marks)

63.	Wine is an aqueous solution of ethanol with traces of other organic compounds which give the wine its characteristic flavour and aroma. Once opened, oxidation of the ethanol in the wine produces ethanoic acid.
•	A white wine with an ethanol concentration of 2.25 mol dm–3 was opened and allowed to stand at room temperature for 2 weeks.
•	A 25.0 cm3 sample of the wine was transferred to a clean conical flask and phenolphthalein indicator added.
•	Aqueous sodium hydroxide of concentration 0.205 mol dm–3 was added from a burette until the colour of the indicator changed.
•	The titration was repeated and the titre values in cm3 were 26.35, 26.90 and 26.45.
	The equation for the neutralisation reaction is
	CH3COOH + NaOH → CH3COONa + H2O
 
(a)	(i)	Name the piece of apparatus used to measure 25.0 cm3 of wine.
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(1)
 
(ii)	State how the burette should be rinsed.
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(1)
 
(iii)	State the colour change at the end-point.
From ...................................................... to ......................................................
(2)

(b)	(i)	Explain, by reference to appropriate error limits, what is meant by the term concordant results.
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(1)

(ii)	Calculate the mean (average) titre which will be used to calculate the concentration of ethanoic acid.

(1)
(iii)	Calculate the number of moles of sodium hydroxide reacting with 25.0 cm3 of the wine.

(1)
(iv)	Hence calculate the concentration of the ethanoic acid, in mol dm–3.

(2)
(v)	Calculate the percentage of the ethanol that has oxidised, given that one mole of ethanol forms one mole of ethanoic acid.

(1)
(c)	Suggest why this method would not be effective for the analysis of the acid content of a red wine.
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(1)
(Total 11 marks)

64.	(a)	The diagram shows the type of bonding present in the elements lithium and sodium in the solid state.

(i)	What name is given to this type of bonding?
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(1)
 
(ii)	Suggest why the melting point of lithium is greater than that of sodium.
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(2)
 
(b)	Lithium can react with chlorine to produce lithium chloride. When a sample of lithium chloride is heated in a Bunsen flame, a red colour is seen.
(i)	Draw a ‘dot and cross’ diagram of lithium chloride showing all the electrons.
Indicate the charges clearly on your diagram.

(2)
 
(ii)	Describe the changes that occur within the lithium ion to produce the flame colour.
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(2)
 
(iii)	Name ONE other metallic element whose compounds produce a red coloured flame.
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(1)
(Total 8 marks)

65.	(a)	(i)	What condition is necessary to make a solution containing a mixture of potassium iodate, KIO3, and potassium iodide from iodine and 4.0 mol dm–3 potassium hydroxide solution?
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(1)
 
(ii)	State the oxidation number of iodine in
iodine ...............
potassium iodate, KIO3 ...............
potassium iodide ...............
(2)

(iii)	Write a balanced equation, with state symbols, for the reaction between iodine and potassium hydroxide solution.

(2)
 
(iv)	Explain why this is classified as a disproportionation reaction.
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(1)
 
(b)	The purity of a sample of potassium iodate, KIO3, can be found by reacting it in aqueous solution with two chemicals to form iodine. The quantity of iodine formed can then be found by titration.
(i)	Name these two chemicals.
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(2)
 
(ii)	Name the solution used to determine the iodine concentration by titration.
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(1)
 
(iii)	Name the indicator used in this titration and state the colour change.
Indicator .....................................................................................................
From ................................................... to ...................................................
(2)
(Total 11 marks)

66.	Which concentrated acid should be used to dissolve a carbonate of a Group 2 metal to carry out a flame test?
A	ethanoic acid
B	hydrochloric acid
C	nitric acid
D	sulfuric acid
(Total 1 mark)

67.	What colour does a barium salt give in a flame test?
A	colourless
B	green
C	red
D	yellow-red
(Total 1 mark)

68.	Separate flame tests are carried out with lithium, sodium, potassium, magnesium, calcium and strontium salts. How many of these metal ions would colour the flame red?
A	1
B	2
C	3
D	4
(Total 1 mark)

69.	A Group 2 element reacts vigorously with water to produce a soluble hydroxide, which forms a white precipitate when neutralised by sulfuric acid and forms a carbonate which is very stable to heat. The element could be
A	magnesium
B	calcium
C	strontium
D	barium
(Total 1 mark)

70.	The Group 2 metals, considered in order of increasing atomic number, show a decrease in
A	first ionisation energy
B	nuclear charge
C	chemical reactivity
D	ionic radius
(Total 1 mark)

71.	When a Group 1 metal nitrate is heated, brown fumes are observed. The metal could be
A	lithium
B	sodium
C	rubidium
D	caesium
(Total 1 mark)

72.	Methyl orange is red in acidic solutions and yellow in alkaline solutions. What is the colour of the indicator at the end point of a titration of aqueous sodium hydroxide solution with hydrochloric acid?
A	red
B	pink
C	orange
D	yellow
(Total 1 mark)

73.	The volume, in cm3, of 0.25 mol dm–3 hydrochloric acid required to neutralise 100 cm3 of 0.125 mol dm–3 barium hydroxide solution, Ba(OH)2(aq), is
A	25
B	50
C	100
D	200
(Total 1 mark)

74.	Which of the following statements is FALSE?
A	iodine is more electronegative than bromine.
B	fluorine is more electronegative than chlorine.
C	metallic elements tend to react by loss of electrons.
D	chlorine is more electronegative than sulfur.
(Total 1 mark)

75.	A commercial production of iodine involves the reduction of a solution of iodate(V) ions, IO3–, with hydrogen sulfite ions, HSO3–. The equation for the reaction may be written
xIO3– + yHSO3–  zSO42– + I2 + 3H+ + H2O
	What are the balancing numbers x, y and z?
A	5,2,2
B	2,5,2
C	2,5,5
D	5,5,2
(Total 1 mark)

76.	Chlorine was used in swimming pools as a bactericide.
	The amount of chlorine present can be determined by adding excess potassium iodide solution to a known volume of swimming pool water. This reacts to form iodine:
	Cl2(aq) + 2I–(aq) ® I2(aq) + 2Cl–(aq)
	The amount of iodine formed is then found by titration with sodium thiosulfate solution of known concentration.
	The ionic equation for the reaction between iodine and sodium thiosulfate in aqueous solution is
	I2(aq) + 2S2O32–(aq) ® S4O62–(aq) + 2I–(aq)
	A student carried out the determination of chlorine in a sample of swimming pool water.
A record of the measurements obtained is given below:
Volume of water sample tested	=	1000 cm3
Final reading of burette	=	16.3 cm3
Initial reading of burette	=	7 cm3
Volume added from burette	=	9.3 cm3
	Concentration of sodium thiosulfate solution	=	0.00500 mol dm–1

(a)	(i)	The record of measurements reveals faults both in the procedure and the recording of measurements. State one fault in each of these.
Procedure .........................................................................................................
Recording of measurements .............................................................................
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(2)
 
(ii)	Calculate the number of moles of sodium thiosulfate used in the titration.

(1)
 
(iii)	Use your answer to (ii) to calculate the number of moles of iodine which reacted.

(1)
(iv)	Deduce the concentration of chlorine, in mol dm–3, in the swimming pool water.

(1)

(b)	The disinfecting action of chlorine in swimming pools is due to the presence of chloric(I) acid, HClO, formed by the reaction of chlorine with water.
	In many swimming pools, chemicals other than chlorine are used to form chloric(I) acid. This is partly because the use of chlorine gas causes much more corrosion of metal parts in swimming pools than does chloric(I) acid.
	Compounds used to chlorinate swimming pool water in this way include calcium chlorate(I) and chlorine dioxide.
(i)	State and explain the type of reaction that occurs when chlorine attacks a metal, using the example of iron.
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(2)
 
(ii)	Suggest one other reason why the use of chlorine is undesirable in swimming pools.
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(1)
 
(iii)	Give the formula for calcium chlorate(I).
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(1)
 
(iv)	Chlorine dioxide, ClO2, undergoes a disproportionation reaction when it reacts with water.
	4ClO2 + 2H2O ® HClO + 3HClO3
	Explain, in terms of oxidation numbers, why this is a disproportionation reaction.
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(2)
 
(c)	Discuss and explain the science community’s advice that CFCs should no longer be used in aerosols, foams and refrigerants. Support your answer with one or more equations.
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(6)
(Total 17 marks)