AS LEVEL CHEMISTRY

PAPER 2
PRACTICE PAPER 18
(structured questions only)
Answer all questions
Max 80 marks

	
Name		……………………………………………………………..

	
Mark		……../80	……....%	Grade ………
		
Note – this paper only contains structured questions

1.		

		
(Total 9 marks)
2.          The alkane butane is used as a fuel.
(a)     (i)      Write an equation for the complete combustion of butane.
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(1)
(ii)     State a condition which may cause carbon to be formed as a product in the combustion of butane.
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(1)
(b)     Butane obtained from crude oil may contain trace amounts of an impurity.
When this impurity burns it produces a toxic gas that can be removed by reacting it with calcium oxide coated on a mesh.
(i)      Suggest the identity of the toxic gas.
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(1)
(ii)     Suggest why calcium oxide reacts with the toxic gas.
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(1)
(iii)     Suggest why the calcium oxide is coated on a mesh.
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(1)
(Total 5 marks)
 
3.	Some oil-fired heaters use paraffin as a fuel.
One of the compounds in paraffin is the straight-chain alkane, dodecane (C12H26).
(a)     Give the name of the substance from which paraffin is obtained.
State the name of the process used to obtain paraffin from this substance.
Substance ......................................................................................................
Process ..........................................................................................................
(2)
(b)     The combustion of dodecane produces several products.
Write an equation for the incomplete combustion of dodecane to produce gaseous products only.
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(1)

(c)     Oxides of nitrogen are also produced during the combustion of paraffin in air.
(i)      Explain how these oxides of nitrogen are formed.
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(2)
(ii)     Write an equation to show how nitrogen monoxide in the air is converted into nitrogen dioxide.
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(1)
(iii)     Nitric acid (HNO3) contributes to acidity in rainwater.
Deduce an equation to show how nitrogen dioxide reacts with oxygen and water to form nitric acid.
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(1)
(d)     Dodecane (C12H26) can be cracked to form other compounds.
(i)      Give the general formula for the homologous series that contains dodecane.
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(1)
(ii)     Write an equation for the cracking of one molecule of dodecane into equal amounts of two different molecules each containing the same number of carbon atoms.
State the empirical formula of the straight-chain alkane that is formed.
Name the catalyst used in this reaction.
Equation ...............................................................................................
Empirical formula of alkane ..................................................................
Catalyst .................................................................................................
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(3)
(iii)     Explain why the melting point of dodecane is higher than the melting point of the straight-chain alkane produced by cracking dodecane.
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(2)

(e)     Give the IUPAC name for the following compound and state the type of structural isomerism shown by this compound and dodecane.
 
IUPAC name ..................................................................................................
Type of structural isomerism .........................................................................
(2)
(f)     Dodecane can be converted into halododecanes.
Deduce the formula of a substance that could be reacted with dodecane to produce 1-chlorododecane and hydrogen chloride only.
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(1)
(Total 16 marks)

4.	The carboxylic acid 3-methylbutanoic acid is used to make esters for perfumes.
The following scheme shows some of the reactions in the manufacture of this carboxylic acid.
 
(a)     One of the steps in the mechanism for Reaction 1 involves the replacement of the functional group by bromine.
(i)      Use your knowledge of organic reaction mechanisms to complete the mechanism for this step by drawing two curly arrows on the following equation.

(2)
(ii)     Deduce the name of the mechanism in part (i).
Give the IUPAC name of (CH3)2CHCH2Br
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(2)
(b)     Reaction 3 is an acid-catalysed reaction in which water is used to break chemical bonds when the CN functional group is converted into the COOH functional group.
Infrared spectroscopy can be used to distinguish between the compounds in this reaction.
Deduce the name of the type of reaction that occurs in Reaction 3.
Identify one bond in (CH3)2CHCH2CN and a different bond in (CH3)2CHCH2COOH that can be used with infrared spectroscopy to distinguish between each compound.
For each of these bonds, give the range of wavenumbers at which the bond absorbs.
Use Table A on the Data Sheet when answering this question.
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 (3)
(c)     When 3-methylbutanoic acid reacts with ethanol in the presence of an acid catalyst, an equilibrium is established. The organic product is a pleasant-smelling ester.
 
 	(CH3)2CHCH2COOH   +   CH3CH2OH     	(CH3)2CHCH2COOCH2CH3
                an ester	+   H2O	

The carboxylic acid is very expensive and ethanol is inexpensive. In the manufacture of this ester, the mole ratio of carboxylic acid to ethanol used is 1 to 10 rather than 1 to 1.
(i)      Use Le Chatelier’s principle to explain why a 1 to 10 mole ratio is used. In your explanation, you should not refer to cost.
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 (3)
(ii)     Explain how a catalyst increases the rate of a reaction.
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 (2)
(Total 12 marks)

5.      Alkanes are saturated hydrocarbons which can be obtained from crude oil.
Pentane is an example of an alkane. A molecule of pentane contains five carbon atoms.
(a)     (i)      State the meaning of the term saturated and of the term hydrocarbon as applied to alkanes.
Saturated ............................................................................................
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Hydrocarbon .......................................................................................
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(2)
(ii)     Give the general formula for the alkanes.
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(1)
(b)     Pentane burns completely in oxygen.
(i)      Write an equation for this reaction.
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(1)
(ii)     State how the products of this reaction may affect the environment.
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(1)
(c)     Give the name of a solid pollutant which may form when pentane burns incompletely in air.
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(1)

(d)    One molecule of C9H20 can be cracked to form one molecule of pentane and one other product.
(i)      Write an equation for this cracking reaction. 
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(1)
(ii)     Suggest a type of compound that can be manufactured from the other product of this cracking reaction.
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(1)
(iii)     State why a high temperature is needed for cracking reactions to occur.
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(1)
(e)     Pentane can react to form the following haloalkane Q.

(i)      Name Q.
 
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(1)
(ii)     State the type of structural isomerism shown by Q and the haloalkane shown below.

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(1)
(Total 11 marks)

Topic 7 – 4 (W7-3-6b)

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 (Total 4 marks)
8.

	
(Total 8 marks)

9.		

(Total 15 marks)