1.	Cars are fitted with catalytic converters in order to reduce the pollution caused by the combustion of petrol.  Potential pollutant gases include carbon monoxide, nitrogen monoxide and unburnt hydrocarbons.  The first two compounds are removed by passing the hot gases over a platinum catalyst.
CO(g) + NO(g) ® CO2(g) + N2(g)     DH = –373 kJ mol–1
In the absence of a catalyst, this reaction is extremely slow.
 
(a)	(i)	Define the term activation energy.
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(1)
 
(ii)	Comment on the relative value of the activation energy of this reaction compared with the much faster reaction of nitrogen monoxide with oxygen.
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(1)
 
(b)	(i)	Draw a distribution of the molecular energies of gas molecules at two different temperatures, T1 and a higher temperature T2.  Label the curves T1 and T2 and mark the energy corresponding to the activation energy, EA.

(3)

(ii)	Use the diagram to explain why the rate of a reaction, such as that between carbon monoxide and nitrogen monoxide, will change as the temperature increases.
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(2)
 
(c)	The reaction between carbon monoxide and nitrogen monoxide requires a platinum catalyst with a large surface area.  Explain the effect of a catalyst on the rate of this reaction and why the surface area needs to be large.
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(4)
(Total 11 marks)

2.	The rate of any chemical reaction is increased if the temperature is increased. 
(a)	Draw a diagram to represent the Maxwell-Boltzmann distribution of molecular energies at a temperature T1 and at a higher temperature T2.

 (3)
 
(b)	Use your diagram and the idea of activation energy to explain why the rate of a chemical reaction increases with increasing temperature.
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(4)
(Total 7 marks)

3.	In a series of experiments to investigate the factors which control the rate of a chemical reaction, aqueous hydrochloric acid was added to calcium carbonate in a conical flask placed on an electronic balance.
The loss in mass of the flask and its contents was recorded for 15 minutes.
CaCO3(s) + 2HCl(aq) ® CaCl2(aq) + H2O(l) + CO2(g)
 
	Four experiments were carried out.
Experiments 1, 3 and 4 were carried out at room temperature (20 °C).
The same mass of calcium carbonate (a large excess) was used in each experiment.
The pieces of calcium carbonate were the same size in Experiments 1, 2 and 4.
Experiment	Calcium carbonate	Hydrochloric acid	
1	Small pieces	50.0 cm3  of 1.00 mol dm–3	
2	Small pieces	50.0 cm3  of 1.00 mol dm–3 heated to 80°C	
3	One large piece	50.0 cm3  of 1.00 mol dm–3	
4	Small pieces	50.0 cm3  of 2.00 mol dm–3	
 
(a)	The results of Experiment 1 give the curve shown on the graph below.

(i)	Explain why there is a loss in mass as the reaction proceeds.
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(2)

(ii)	Explain the shape of the curve drawn for Experiment 1.
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(2)
(b)	Draw curves on the graph to represent the results you would expect for Experiments 2, 3 and 4. Label the curves 2, 3 and 4.
(3)
 
(c)	(i)	Calculate the mass of calcium carbonate which exactly reacts with 50.0 cm3 of 1.00 mol dm–3 aqueous hydrochloric acid. Mr(CaCO3) = 100.

(3)
 
(ii)	Based on your answer to (c)(i) suggest a suitable mass of calcium carbonate to use in the experiments. Explain your answer.
Suggested mass: ...............................................................................................
Explanation: .....................................................................................................
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(2)
(Total 12 marks)

4.	(a)	(i)	State two factors other than a change in temperature or the use of a catalyst that influence the rate of a chemical reaction.
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(2)
 
(ii)	For one of the factors you have chosen explain the effect on the rate.
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(2)
 
(b)	The Maxwell–Boltzmann distribution of molecular energies at a given temperature T1 is shown below.

(i)	On the same axes draw a similar curve for a reaction mixture at a higher temperature T2.
(2)
 
(ii)	Place a vertical line marked Ea at a plausible value on the energy axis to represent the activation energy for a reaction.
(1)

(iii)	Use your answers to parts (i) and (ii) to explain why an increase in temperature causes an increase in the reaction rate.
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(3)
(Total 10 marks)

5.	(a)	A mixture of hydrogen iodide, hydrogen and iodine (all in the gaseous state) establishes dynamic equilibrium if a constant temperature is maintained.
2HI (g)     H2 (g) + I2 (g)                      ΔH = +9.6 kJ mol–1
(i)	Explain the meaning of the term dynamic equilibrium.
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(2)
 
(ii)	How, if at all, would the proportion of hydrogen iodide present at equilibrium change if the temperature were to be increased? Justify your answer.
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(2)

(iii)	The reaction is catalysed by metals such as gold and platinum. How, if at all, would the proportion of hydrogen iodide present at equilibrium change if the reaction were to be catalysed? Justify your answer.
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(1)
 
(b)	Part of an energy profile for this reaction is shown below. It is not intended to be to scale.

	Complete the profile showing:
·	the products;
·	the progress of both uncatalysed and catalysed reactions;
·	labelled arrows to indicate the activation energies of both the uncatalysed and catalysed reactions.
(4)
(Total 9 marks)

6.	(a)	(i)	Draw a diagram to represent the Maxwell-Boltzmann distribution of molecular energies at a temperature T.

(2)
 
(ii)	Catalysts are used in the exhausts of modem motor cars to speed up the reaction between polluting gases (carbon monoxide, CO, and dinitrogen oxide, N2O) before they reach the end of the exhaust pipe.
	Use the diagram in (a)(i) to explain how the catalyst achieves this.
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(4)

(b)	State ONE other method of increasing the rate of the reaction between two gases in general. Explain how the collision theory supports your suggested method.
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(3)
(Total 9 marks)

7.	An alcohol, X, has the molecular formula C4H10O.
(a)	X reacts with sodium, forming bubbles of a colourless gas.
	Write a balanced equation for the reaction.

(2)
 
(b)	When X is heated under reflux with a mixture of sodium dichromate(VI) solution and concentrated sulphuric acid, a green solution forms.
(i)	Give the formula of the ion responsible for the green colour of the solution.
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(1)

(ii)	Draw a labelled diagram of the apparatus used to reflux the mixture.

(3)
 
(iii)	A colourless organic liquid, Y, is distilled from the green solution.
	This liquid will not neutralise sodium carbonate solution, and it will not react with Benedict’s solution.
	Draw the displayed formula of Y and state its name.
	Displayed formula

	Name ....................................................................................................................
(2)
 
(iv)	Deduce the structural formula of X.
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(1)
(Total 9 marks)

8.	The equation below shows a possible reaction for producing methanol.
CO(g) + 2H2(g) ® CH3OH(l)	ΔHο = -129 kJ mol–1
 
(a)	The entropy of one mole of each substance in the equation, measured at 298 K, is shown below.
Substance	Sο
/J mol-1 K-1	
CO(g)	197.6	
H2(g)	130.6	
CH3OH(l)	239.7	
 
(i)	Suggest why methanol has the highest entropy value of the three substances.
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(1)
 
(ii)	Calculate the entropy change of the system, ΔSοsystem, for this reaction.

(2)
 
(iii)	Is the sign of ΔSοsystem as expected? Give a reason for your answer.
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(1)

(iv)	Calculate the entropy change of the surroundings ΔSοsurroundings, at 298 K.

(2)
 
(v)	Show, by calculation, whether it is possible for this reaction to occur spontaneously at 298 K.

(2)
 
(b)	When methanol is produced in industry, this reaction is carried out at 400 ºC and 200 atmospheres pressure, in the presence of a catalyst of chromium oxide mixed with zinc oxide. Under these conditions methanol vapour forms and the reaction reaches equilibrium. Assume that the reaction is still exothermic under these conditions.
CO(g) + 2H2(g)    CH3OH(g)
(i)	Suggest reasons for the choice of temperature and pressure.
Temperature ........................................................................................................
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Pressure ...............................................................................................................
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(3)

(ii)	The catalyst used in this reaction is heterogeneous. Explain this term.
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(1)
 
(iii)	Write an expression for the equilibrium constant in terms of pressure, Kp, for this reaction.
CO(g) + 2H2(g)  CH3OH(g)

(1)
 
(iv)	In the equilibrium mixture at 200 atmospheres pressure, the partial pressure of carbon monoxide is 55 atmospheres and the partial pressure of hydrogen is 20 atmospheres.
	Calculate the partial pressure of methanol in the mixture and hence the value of the equilibrium constant, Kp. Include a unit in your answer.

(2)

(c)	The diagram below shows the distribution of energy in a sample of gas molecules in a reaction when no catalyst is present. The activation energy for the reaction is EA.

(i)	What does the shaded area on the graph represent?
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(1)
(ii)	Draw a line on the graph, labelled EC, to show the activation energy of the catalysed reaction.
(1)
(Total 17 marks)

9.	(a)	The distribution of the energy of particles in a gas at temperature T1 is shown below.

(i)	On the diagram above, draw the distribution of energy of particles at a lower temperature, T2.
(2)
 
(ii)	Use the diagram to explain why the rate of a reaction increases with an increase in temperature.
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(3)

(iii)	Explain fully why a catalyst increases the rate of a reaction.
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(2)

(b)	The fermentation of glucose is an exothermic reaction and is catalysed by enzymes in yeast.
C6H12O6(aq) → 2C2Η5ΟΗ(aq) + 2CO2(g)
	The reaction is slow at room temperature.
(i)	Describe, with the aid of a diagram, an experiment you could do to follow the progress of this reaction at different temperatures.

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(4)

(ii)	Would you expect ∆Ssystem to be positive or negative for this reaction? Justify your answer with TWO pieces of evidence.
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(2)
 
(iii)	Deduce the sign of ∆Ssurroundings. Show your reasoning.
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(2)
(Total 15 marks)

10.	Hydrogen peroxide decomposes according to
2H2O2(aq) → 2H2O(l) + O2(g)
	The reaction is catalysed by solid manganese(IV) oxide, MnO2.
(a)	Two experiments are carried out under the same conditions except that in one experiment the manganese(IV) oxide is a fine powder and in the other the same mass of coarse granules is used.
	Which experiment would show the faster rate of decomposition? Explain your answer in terms of collision theory.
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(2)
 
(b)	(i)	Draw a labelled Maxwell-Boltzmann distribution of molecular energies in a mixture of gases at two different temperatures T1 and T2, where T2 is higher than T1.

(4)

(ii)	Mark on your graph a suitable value for the activation energy, Ea, for the reaction between the gases. Use your drawing to account for the increase in reaction rate with increasing temperature.
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(3)
 
(iii)	Use the Maxwell-Boltzmann distribution to explain why a catalyst increases the rate of a reaction at temperature T1.
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(2)
(Total 11 marks)

11.	(a)	(i)	Draw a Maxwell-Boltzmann distribution of molecular energies in a gas at a temperature T.
	
(2)

(ii)	Add a curve to your diagram to show the distribution at a higher temperature and label it TH.
(1)
 
(iii)	Mark on your diagram a line at a suitable place for the activation energy, Ea, for a reaction.
(1)
 
(b)	(i)	Use your answer to (a) to explain, in terms of the frequency and energy of collisions, why an increase in temperature increases the rate of a reaction.
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(4)
 
(ii)	Suggest whether the frequency of the collisions or the energy of collisions is more important in increasing the rate.
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(1)
(Total 9 marks)

12.	This question is about some of the chemicals used in car engines and their reactions.
(a)	Compound X, shown below, is one component of petrol.
	
(i)	Name X.
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(1)
(ii)	Give the empirical formula of X.
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(1)
(iii)	X can be made by cracking decane, C10H22.
	Assuming only one other product forms in a cracking reaction, deduce the molecular formula of this other product.

(1)
 
(iv)	What is the sign of the enthalpy change for the reaction in which decane is cracked? Give a reason for your answer.
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(1)

(v)	If the air supply in a car engine is poor, there is not enough air for carbon dioxide to be produced.
	Use this information to suggest ONE possible equation for the combustion of X in this engine. Use the molecular formula of X in your equation.

(2)
 
(b)	When air enters a car engine, as well as the fuel burning, nitrogen and oxygen can react to form nitrogen(II) oxide.
	N2(g) + O2(g)  2NO(g)	ΔH = + 180 kJ mol–1
(i)	What, if any, is the effect on the percentage of nitrogen(II) oxide in an equilibrium mixture of these three gases if the pressure and temperature are increased?
Explain your answers.
	Increase in pressure
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	Increase in temperature
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(2)
 
(ii)	In a car exhaust pipe, nitrogen(II) oxide passes over a catalytic converter.
The following reaction occurs.
	2NO(g) + 2CO(g) → N2(g) + 2CO2(g)	ΔH = –746 kJ mol–1
	Explain why this reaction speeds up when the car engine has been running for a few minutes.
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(1)
 
(iii)	A textbook says “The catalytic converter converts the gases coming out of the engine into less harmful ones”.
	State, with a reason, which of the four gases in the equation in (ii) you consider to be least harmful.
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(1)
 
(iv)	The diagram below shows the reaction profile for the change which occurs in the catalytic converter.

	On the diagram, show the activation energy, EA.
	Add a line showing the reaction profile if no catalyst is present.
(2)
(Total 12 marks)

13.	This question is about ammonia, NH3, which is produced as shown in the following equation.
	N2(g) + 3H2(g)  2NH3(g)
(a)	Use oxidation numbers to explain why this is a redox reaction.
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(2)
 
(b)	(i)	Use the average (mean) bond enthalpy data to calculate a value for the enthalpy change for this reaction. You are reminded to show all your working.
Bond	Average bond enthalpy
/ kJ mol–1	
N≡N	944	
H—H	436	
N—H	388	

(3)
 
(ii)	The actual standard enthalpy change for this reaction is –92 kJ mol–1. Explain why the value you calculated in (b)(i) is not the same as this.
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(1)

(iii)	At room temperature, a mixture of nitrogen and hydrogen is thermodynamically unstable with respect to ammonia, but is kinetically stable.
	Use the data in (b)(i) and (ii) to help you explain why this mixture is
	thermodynamically unstable
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	kinetically stable
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(3)

(c)	The manufacturer of ammonia would like to achieve a high rate of reaction and a high equilibrium yield of product.
(i)	State and explain, in terms of collision theory, TWO ways to increase the rate of the reaction. An increase in pressure does not alter the rate in this process.
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(6)

(ii)	State and explain TWO ways to increase the equilibrium yield of ammonia.
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(4)
(Total 19 marks)

14.	This question is about the manufacture of sulphuric acid, H2SO4.
(a)	The first stage in the manufacture of sulphuric acid is the combustion of sulphur.
	The following equation shows the reaction taking place when the standard enthalpy of combustion of sulphur is measured.
	S(s) + O2(g) → SO2(g)
	Define the term standard enthalpy of combustion.
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(3)

(b)	In the second stage of the manufacture of sulphuric acid, sulphur dioxide is oxidised to sulphur trioxide as shown in the following equation:
	2SO2(g) + O2(g)  2SO3(g)	ΔH = –196 kJ mol–1
(i)	Explain, in terms of collision theory, why the rate of a reaction is increased by increasing the temperature and by the addition of a catalyst.
Temperature
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Catalyst
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(4)
 
(ii)	State and explain the effect, if any, of increasing the temperature on the equilibrium yield of sulphur trioxide.
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(2)
 
(iii)	State and explain the effect, if any, of an increased pressure on the equilibrium yield of sulphur trioxide.
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(2)
 
(c)	The following equation represents the overall reaction for the manufacture of sulphuric acid from sulphur, oxygen and water.
	2S(s) + H2O + 3O2 ® 2H2SO4(l)
	Use the data below to calculate the enthalpy change for this reaction.
Substance	ΔHfο
/ kJ mol–1	
H2O (l)	–286	
H2SO4 (l)	–814	

(2)
(Total 13 marks)

15.	(a)	This part of the question is about the hydrolysis of halogenoalkanes.
	2 cm3 of ethanol is added to each of three separate test-tubes.
	Three drops of 1-chlorobutane are added to the first, three drops of 1-bromobutane to the second, and three drops of 1-iodobutane are added to the third test-tube.
	2 cm3 portions of hot aqueous silver nitrate solution are added to each test-tube.
	A precipitate forms immediately in the third test-tube, slowly in the second testtube and extremely slowly in the first test-tube. In each reaction the precipitate is formed by silver ions, Ag+(aq), reacting with halide ions formed by hydrolysis of the halogenoalkane.
(i)	Why was ethanol added to each test-tube?
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(1)
 
(ii)	The mechanism of this reaction is similar to that of the reaction between halogenoalkanes and aqueous hydroxide ions.
	What feature of a water molecule enables it to act as a nucleophile in this reaction?
Suggest the mechanism for the reaction between water and 1-iodobutane. (You may represent 1-iodobutane as RCH2I).
Feature of water molecule
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Mechanism

(4)
 
(iii)	What is the colour of the precipitate in the third test-tube?
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(1)

(iv)	Name the precipitate which forms slowly in the first test-tube.
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(1)
 
(v)	Ammonia solution is added to the precipitate in the first test-tube. Describe what you would observe.
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(1)
 
(vi)	Suggest, why the rates of hydrolysis of the three halogenoalkanes are different, in terms of bonding and kinetics.
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(3)
 
(b)	One method of the manufacture of alcohols is to react steam with an alkene.
For example
C2H4(g) + H2O(g)  C2H5OH(l)
	Suggest TWO reasons why this method is preferred to the hydrolysis of halogenoalkanes.
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(2)

(c)	1-bromobutane reacts with an ethanolic solution of potassium hydroxide on heating to form but-1-ene. A diagram of the apparatus that could be used to carry out this reaction and to collect the gaseous but-1-ene is shown below.

(i)	State the hazard when the heating is stopped.
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(1)
(ii)	How would you minimise the risk associated with this hazard?
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(1)
(Total 15 marks)