AS LEVEL CHEMISTRY

PAPER 2
PRACTICE PAPER 13
(structured questions only)
Answer all questions
Max 80 marks

	
Name		……………………………………………………………..

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

1.     (a)     Nitromethane, CH3NO2, is used as an ‘energy rich’ fuel for motor-racing. It burns in oxygen forming three gases.
2CH3NO2(l) + 1½O2(g) → 2CO2(g) + 3H2O(g) + N2(g)
(i)      A 1.00 mol sample of nitromethane was burned in oxygen forming the products shown in the equation above. Calculate the total volume of gases produced at 298 K and 100 kPa (assume that the water is gaseous).
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(ii)     This combustion reaction is very exothermic and reaches a temperature of 1000 K. Determine the total volume of gases when the temperature is raised to 1000 K at a constant pressure.
(If you have been unable to determine a volume in your answer to part (a)(i), you may assume it to be 8.61 × 10–4 m3 but this is not the correct answer).
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(5)
(b)     It has been suggested that, instead of releasing it into the atmosphere, the carbon dioxide gas evolved during a combustion reaction can be absorbed by sodium hydroxide solution, as shown by the following equation.
2NaOH(aq) + CO2(g) → Na2CO3(aq) + H2O(l)
(i)      Give two reasons why this reaction might not be suitable for the removal of carbon dioxide from the exhaust gases of an engine.
Reason 1 ............................................................................................
Reason 2 ............................................................................................
(ii)     The sodium hydroxide solution for this reaction can be made on an industrial scale, together with chlorine gas and hydrogen gas, by electrolysis of a dilute solution of sodium chloride. Suggest one commercial advantage and one environmental disadvantage of this industrial process.
Commercial advantage .......................................................................
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Environmental disadvantage ..............................................................
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(4)

(c)     Nitrogen forms several different oxides. Calculate the empirical formula of an oxide of nitrogen which contains 26% of nitrogen by mass.
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(3)
(d)     Another oxide of nitrogen, N2O, decomposes on warming to produce nitrogen and oxygen. Write an equation for the decomposition reaction.
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(1)
(e)     Internal combustion engines burn fuels in air. Suggest one advantage of using air mixed with N2O for this purpose.
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(1)
(Total 14 marks)
 
2.     (a)     Hydrogen used in the Haber Process is produced in the following dynamic equilibrium reaction.
CH4(g)   +   H2O(g)      CO(g)   +   3H2(g)
(i)      In terms of rates and of concentrations, what does the term dynamic equilibrium mean?
Rates ..................................................................................................
Concentrations …................................................................................
(ii)     State how an increase in pressure will affect the equilibrium yield of hydrogen. Explain your answer.
Equilibrium yield .................................................................................
Explanation .........................................................................................
(iii)     The equilibrium yield of hydrogen is reduced when the reaction is carried out at a lower temperature. What can be deduced about the enthalpy change in this reaction?
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(iv)    Explain why the equilibrium yield is unchanged when a catalyst is introduced.
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(8)

(b)     Ammonia is produced in the Haber Process according to the following equation.
N2(g)   +   3H2(g)    2NH3(g)                           ΔHf = –92 kJ mol–1
Typical operating conditions are 450 °C and 20 MPa (200 bar).
(i)      Explain why 450 °C is a compromise temperature.
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(ii)     Explain why 20 MPa is a compromise pressure.
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 (6)
(Total 14 marks)

3.	The refrigerant R410A, used in air conditioners, is a mixture of two fluoroalkanes, pentafluoroethane and difluoromethane.
(a)    (i)      The mechanism for the reaction of fluorine with either an alkane or a fluoroalkane is similar to that for the reaction of chlorine with methane.
Name the type of mechanism for the reaction of chlorine with methane.
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(1)
(ii)     Write equations for the following steps in the mechanism for the reaction of fluorine with fluoromethane (CH3F) to form difluoromethane (CH2F2).
Initiation step
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First propagation step
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Second propagation step
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A termination step leading to the formation of 1,2-difluoroethane.
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(4)
(iii)    Write an overall equation for the reaction of fluorine with ethane to form pentafluoroethane (CF3CHF2) by this mechanism.
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(1)
(b)     The refrigerant R112A (CCl3CF2Cl) has been banned because of concerns about ozone depletion.
Give the IUPAC name for CCl3CF2Cl
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(1)

(c)     Nitrogen monoxide (NO) catalyses the decomposition of ozone into oxygen.
(i)      Write the overall equation for this decomposition.
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(1)
(ii)     Use the overall equation to deduce Step 3 in the following mechanism that shows how nitrogen monoxide catalyses this decomposition.
Step 1 O3  O + O2
Step 2 NO + O3  NO2 + O2
Step 3 ...................................................................................................
(1)
(Total 9 marks)

4.     (a)     Bromomethane, CH3Br, can be formed by a reaction between bromine and methane.
The mechanism for this reaction is similar to the mechanism for the chlorination
of methane.
(i)      Name the mechanism for this reaction.
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(ii)     Give the name of, and state an essential condition for, the first step in the mechanism for this reaction.
Name ..................................................................................................
Essential condition ..............................................................................
(iii)     Write an equation for a termination step in the mechanism for this reaction which gives ethane as a product. 
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(iv)    Bromomethane can undergo further substitution. Write an overall equation for the reaction between bromomethane and bromine in which dibromomethane is formed. 
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(5)

(b)     Bromomethane reacts with the nucleophile ammonia according to the following equation.
CH3Br + 2NH3  →  CH3NH2 + NH4Br
(i)      Explain what is meant by the term nucleophile.
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(ii)     Name the organic product of this reaction.
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(iii)     Outline a mechanism for this reaction.

  

 
(6)
(Total 11 marks)

5.     (a)     Propene reacts with hydrogen bromide by an electrophilic addition mechanism forming 2-bromopropane as the major product.
The equation for this reaction is shown below.

(i)      Outline the mechanism for this reaction, showing the structure of the intermediate carbocation formed.

(ii)     Give the structure of the alternative carbocation which could be formed in the reaction between propene and hydrogen bromide.

(5)
(b)     A substitution reaction occurs when 2-bromopropane reacts with aqueous sodium hydroxide.
(i)      Draw the structure of the organic product of this reaction and give its name.
Structure

Name ..................................................................................................
(ii)     Name and outline the mechanism for this reaction.
Name of mechanism ...........................................................................
Mechanism

 

(5)

(c)     Under different conditions, 2-bromopropane reacts with sodium hydroxide to produce propene.
(i)      Name the mechanism for this reaction.
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(ii)     State the role of sodium hydroxide in this reaction.
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(2)
(Total 12 marks)
 
6.	The reaction of butane-1,4-diol with butanedioic acid produces the polymer PBS used in biodegradable packaging and disposable cutlery.
Butanedioic acid is produced by two different processes.
Process 1
•        Aqueous sodium hydroxide reacts with 1,4-dibromobutane to make butane-1,4-diol.
•        Butane-1,4-diol is oxidised to butanedioic acid.
Process 2
•        Glucose reacts with carbon dioxide in the presence of microorganisms to produce butanedioic acid directly.
•        The carbon dioxide used in this process is obtained from a local factory that produces bioethanol.
(a)     Deduce one safety reason and one environmental reason why Process 2 is preferred to Process 1.
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 (2)

(b)     (i)      Name and outline a mechanism for the following reaction that occurs in Process 1.
 
BrCH2CH2CH2CH2Br	+	NaOH		BrCH2CH2CH2CH2OH	+	NaBr	
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(3)
(ii)     The infrared spectra shown are those of three compounds.
Compound A   1,4-dibromobutaneCompound B   butane-1,4-diol
Compound C   butanedioic acid
Identify the compound responsible for each spectrum by writing the correct letter, A, B or C, in the box next to each spectrum.
You may find it helpful to refer to Table 1 on the Data Sheet.

(3)

(c)     In the production of bioethanol, glucose (C6H12O6) is converted into a dilute aqueous solution of ethanol and carbon dioxide.
Give the name of this process and state three essential conditions necessary to produce a good yield of ethanol.
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 (4)
(d)     State the class of alcohols to which the diol butane-1,4-diol belongs.
Identify a suitable reagent or combination of reagents for the conversion of butane-1,4-diol into butanedioic acid (HOOCCH2CH2COOH).
Write an equation for this oxidation reaction using [O] to represent the oxidising agent.
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 (3)
(Total 15 marks)
 
7.     (a)     In industry, ethanol is made from ethene in an acid-catalysed reaction. Name the type of reaction. Write an equation and identify a suitable catalyst for this reaction.
Type of reaction...........................................................................................
Equation.......................................................................................................
Catalyst ........................................................................................................
(3)

(b)     Ethanol burns completely in a plentiful supply of air, but incomplete combustion occurs if the air supply is limited.
(i)      Identify a solid pollutant produced by burning ethanol in a limited supply of air.
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(ii)     Write an equation for the incomplete combustion of ethanol to produce the solid pollutant that you have identified in part (b)(i).
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(2)
(Total 5 marks)