1.	(a)	Boron forms the chloride BCl3. Draw a dot-and-cross diagram for BCl3.

(1)
 
(b)	(i)	Draw the shape of the BCl3 molecule.

(1)
 
(ii)	Explain why BCl3 has this shape.
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(2)
 
(c)	(i)	The B¾Cl bond is polar due to the different electronegativity of the atoms. Explain what is meant by the term electronegativity.
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(2)
(ii)	The B¾Cl bond is polar. Explain why BCl3 is not a polar molecule.
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(2)
(Total 8 marks)

2.	(i)	On the following diagram of a water molecule draw partial charges on each atom to show the bond polarities:

(1)
 
(ii)	Explain why a water molecule has the partial charges you have drawn. 
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(2)
 
(iii)	Explain whether or not a water molecule is polar overall.
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(1)
(Total 4 marks)

3.	Nitrogen and phosphorus are in the same group of the Periodic Table. Phosphorus and hydrogen form the compound phosphine, PH3, and nitrogen and hydrogen form ammonia, NH3.
(a)	(i)	State the number of bond pairs and lone pairs of electrons in a molecule of phosphine.
Bond pairs of electrons: .....................   Lone pairs of electrons: ....................
(2)
 
(ii)	Use your answer to (i) to draw the shape of the molecule and indicate on your diagram the approximate HPH bond angle that you would expect.

(2)
 
(b)	The boiling temperature of ammonia is –33 °C and that of phosphine –88°C.
(i)	List all the intermolecular forces that exist between molecules of ammonia.
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(2)
 
(ii)	Explain why the boiling temperature of phosphine is lower than that for ammonia.
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(2)

(c)	Ammonia forms a dative covalent bond with H+ ions to form the ammonium ion, NH4+.
(i)	Explain what is meant by the term dative covalent bond.
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(2)
 
(ii)	What part of the ammonia molecule enables it to form such a bond?
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(1)
 
(iii)	State and explain the shape of the ammonium ion, NH4+.
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(3)
(Total 14 marks)

4.	Silicon reacts with chlorine to produce silicon tetrachloride, as shown in the following equation
Si(s) + 2Cl2(g) → SiCl4(l)
(a)	(i)	Calculate the mass of silicon tetrachloride obtained from 10.0 g of silicon.

(3)

(ii)	Calculate the minimum volume of chlorine that would be required to react completely with 10.0 g of silicon.
	[1 mol of gas occupies 24.0 dm3 under the conditions of the experiment]

(2)

(b)	Draw a silicon tetrachloride molecule, SiCl4, showing its three-dimensional shape.
Name the shape and state the bond angle. Explain why the molecule has this shape.
	Diagram

	Name of shape .............................................................................................................
	Bond angle ..............................................
	Explanation of shape
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(5)
 
(c)	(i)	Why are silicon-chlorine bonds polar?
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(1)

(ii)	Explain why the silicon tetrachloride molecule has no permanent dipole.
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(2)
(Total 13 marks)

5.	(a)	Draw the ammonia molecule, NH3, making its three-dimensional shape clear. Mark in the bond angle on your diagram. Explain why ammonia has this shape and this bond angle.
	Diagram

	Explanation
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(4)

(b)	Explain whether ammonia is a polar molecule or not.
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(2)
 
(c)	Explain, in terms of the intermolecular forces in both compounds, why ammonia has a higher boiling temperature than phosphine, PH3.
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(3)
 
(d)	(i)	Explain, in terms of electrons, how ammonia can react with hydrogen ions to form ammonium ions, NH4+.
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(2)

(ii)	State the number of protons and the number of electrons present in an ammonium ion.
	number of protons .....................................
	number of electrons....................................
(2)
(Total 13 marks)

6.	(a)	(i)	Explain why a water molecule does not have a linear shape.
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(2)
 
(ii)	State the HOH bond angle in water and explain why it has this value.
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(2)

(b)	(i)	Draw the boron trichloride molecule, BCl3, making its shape clear. Mark in the bond angle on your diagram.

(2)
 
(ii)	Explain why a B–Cl bond is polar.
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(1)
 
(iii)	Explain why a BCl3 molecule is non-polar.
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(1)
 
(iv)	Name the strongest intermolecular force between boron trichloride molecules.
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(1)
 
(c)	A compound of phosphorus and chlorine has the composition by mass shown below.
Element	% by mass	
P	14.9	
Cl	85.1	
	Calculate the empirical formula of this compound.

(2)
(Total 11 marks)

7.	Beryllium chloride, BeCl2, is covalent.
(i)	Use ideas of ion polarisation or electronegativity to suggest why beryllium chloride, a compound of a metal and a non-metal, is covalent rather than ionic.
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(2)

(ii)	Draw a ‘dot and cross’ diagram to show the bonding in a beryllium chloride molecule, BeCl2. In your diagram show all the outer shell electrons in the atoms of beryllium and chlorine.

(1)
(Total 3 marks)

8.	(a)	Cooking fuels and petrol for car engines need to be gases or liquids which vaporise easily. This will be the case if the intermolecular forces are weak.
	Two common fuels are methane, CH4, and 2,2,4-trimethylpentane, C8H18.
	Electronegativity	
carbon	2.1	
hydrogen	2.5	
 
(i)	Explain the meaning of the term electronegativity.
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(2)

(ii)	The C—H bond in methane has some polarity but overall the molecule is non-polar.
	Explain why methane is a non-polar molecule.
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(2)
 
(iii)	Identify the strongest intermolecular force that exists between
2,2,4-trimethylpentane molecules in the liquid state.
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(1)
 
(b)	In a car engine 2,2,4-trimethylpentane burns in air to produce carbon dioxide and water.
	The equation is
	2C8H18 + 25O2 → 16CO2 + 18H2O
	Molar mass of C8H18 = 114 g mol–1
 
(i)	Calculate the volume of oxygen needed to burn 700 g of 2,2,4-trimethylpentane.
[Assume the molar volume of a gas = 24.0 dm3 mol–1]

(3)

(ii)	Calculate the mass of carbon dioxide produced in the reaction in (i).

(2)
(Total 10 marks)

9.	Which of the following species is polar?
A	NH3
B	BF3
C	SO3
D	CO3
(Total 1 mark)

10.	Polar liquids are affected by electric fields. For which of the following liquids would a jet of the liquid be affected by an electric field?
A	hexane
B	cyclohexane
C	cyclohexene
D	cyclohexanol
(Total 1 mark)

11.	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)

12.	(a)	(i)	Name the type of bonding that exists between water molecules.
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(1)
 
(ii)	Draw a diagram to show this bonding. Use displayed formulae of two water molecules. Clearly mark and label the bond angle between the water molecules.

(2)
 
(b)	(i)	Draw the boron trichloride molecule, BCl3, making its shape clear. Mark the bond angle on your diagram.

(2)

(ii)	Explain why boron trichloride has this shape.
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(3)
 
(iii)	Explain why a B–Cl bond is polar.
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(1)
 
(iv)	Explain why a BCl3 molecule is non-polar.
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(1)
 
(v)	Name the strongest intermolecular force between boron trichloride molecules.
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(1)
(Total 11 marks)