A-LEVEL CHEMISTRY

PAPER 3
PRACTICE PAPER 1

Answer all questions
Max 90 marks
1 hour 45 minutes

	
Name		……………………………………………………………..

Mark		……../90	……....%	Grade ………
		
The first 11 multiple choice questions have already been used for AS-level resources

1.     (a)     When chlorine gas dissolves in cold water, a pale green solution is formed. In this solution, the following equilibrium is established.
Cl2(g) + H2O(l)  H+(aq) + Cl–(aq) + HClO(aq)
Give the formula of the species responsible for the pale green colour in the solution of chlorine in water.
Use Le Chatelier’s principle to explain why the green colour disappears when sodium hydroxide solution is added to this solution.
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(3)
(b)     Consider the following reaction in which iodide ions behave as reducing agents.
Cl2(aq) + 2I–(aq) → I2(aq) + 2Cl–(aq)
In terms of electrons, state the meaning of the term reducing agent.
Deduce the half-equation for the conversion of chlorine into chloride ions.
Explain why iodide ions are stronger reducing agents than chloride ions.
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(4)

(c)     When chlorine reacts with water in bright sunlight, only two products are formed. One of these products is a colourless, odourless gas and the other is an acidic solution that reacts with silver nitrate solution to give a white precipitate.
Write an equation for the reaction of chlorine with water in bright sunlight.
Name the white precipitate and state what you would observe when an excess of aqueous ammonia is added to it.
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(3)
(d)     The reaction of chlorine with ethene is similar to that of bromine with ethene.
Name and outline a mechanism for the reaction of chlorine with ethene to form
1,2-dichloroethane, as shown by the following equation.
H2CCH2 + Cl2 → ClCH2CH2Cl

 
 
(5)
(Total 15 marks)

2.      Hydrogen and carbon monoxide were mixed in a 2:1 mole ratio. The mixture was allowed to reach equilibrium according to the following equation at a fixed temperature and a total pressure of 1.75 × 104 kPa.
2H2(g)   +   CO(g)      CH3OH(g)
(a)     The equilibrium mixture contained 0.430 mol of carbon monoxide and 0.0850 mol of methanol.
(i)      Calculate the number of moles of hydrogen present in the equilibrium mixture.
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(ii)     Hence calculate the mole fraction of hydrogen in the equilibrium mixture.
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(iii)     Calculate the partial pressure of hydrogen in the equilibrium mixture.
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(5)
(b)     In a different mixture of the three gases at equilibrium, the partial pressure of carbon monoxide was 7550 kPa, the partial pressure of hydrogen was 12300 kPa and the partial pressure of methanol was 2710 kPa.
(i)      Write an expression for the equilibrium constant, Kp, for this reaction.
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(ii)     Calculate the value of the equilibrium constant, Kp, for the reaction under these conditions and state its units.
Kp ........................................................................................................
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Units ....................................................................................................
(3)

(c)     Two isomeric esters E and F formed from methanol have the molecular formula C6H12O2
Isomer E has only 2 singlet peaks in its proton n.m.r. spectrum.
Isomer F is optically active.
Draw the structures of these two isomers.
Isomer E

 

Isomer F

 

(2)
(Total 10 marks)

3.	Ethanoic acid is manufactured in industry from methanol and carbon monoxide in a multi-step process involving hydrogen iodide. Ethanoic acid is obtained from the reaction mixture by fractional distillation. Methanoic acid is a useful by-product of this process.
The Ka value of an organic acid can be determined by using the pH curve obtained when the acid is titrated against sodium hydroxide. The pH of the solution formed when exactly half of the acid has been neutralised is equal to the pKa value of the acid. The Ka value of the acid can be used to confirm its identity.
A chemist used a pH curve to determine the pKa value of acid Y, formed during the manufacture of ethanoic acid. The chemist transferred 25.0 cm3 of a solution of acid Y into a beaker using a pipette, and measured the pH of the acid solution using a pH meter which could be read to one decimal place. A solution of sodium hydroxide of concentration 0.100 mol dm–3 was added from a burette in small portions. The pH of the mixture was recorded after each addition of the sodium hydroxide solution. The chemist’s results are given in the table below.
 
 	Volume of sodium 
hydroxide solution 
added / cm3	pH		Volume of sodium 
hydroxide solution 
added / cm3	pH	
 	0.0	3.0		23.5	5.1	
 	2.0	3.4		24.0	5.5	
 	4.0	3.5		24.5	11.8	
 	8.0	3.7		25.0	12.1	
 	12.0	4.3		26.0	12.3	
 	16.0	4.1		27.0	12.4	
 	20.0	4.3		28.0	12.5	
 	22.0	4.7		30.0	12.5	
(a)     Use the results given in the table above to plot a graph of pH (y-axis) against volume of sodium hydroxide solution added. Use the points to draw the pH curve, ignoring any anomalous results.
 
(6)
(b)     Use your graph from part (a) to determine the
(i)      volume of sodium hydroxide solution at the end-point of the titration
................... cm3
(ii)     volume of sodium hydroxide solution needed to neutralise half the acid
................... cm3
(iii)    pH of the half-neutralised mixture. Give your answer to one decimal place.
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(3)

(c)     Use the pH of the half-neutralised mixture from part (b) (iii) to calculate the value of the acid dissociation constant, Ka, of the acid Y. Show your working.
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(2)
(d)     The table below shows the Ka values for some organic acids.
 
 	Acid	Ka / mol dm–3	
 	Methanoic acid	1.6 ×10–4	
 	Ethanoic acid	1.7 ×10–5	
 	Iodoethanoic acid	6.8 ×10–4	
 	Propanoic acid	1.3 ×10–5	

Use your answer from part (c) to identify acid Y from this table.
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(1)
(e)     For the pipette and the burette, the maximum total errors are shown below. These errors take into account multiple measurements.
 
 	pipette
burette	± 0.05 cm3
± 0.15 cm3	
Estimate the percentage error in using each of these pieces of apparatus. You should use your answer to part (b) (i) to estimate the percentage error in using the burette.
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(1)
(f)      Calculate the difference between the Ka value from part (c) and the Ka value of the acid you identified as the acid Y in the table in part (d).
Express this difference as a percentage of the value given in the table in part (d). (If you could not complete the calculation in part (c), you should assume that the Ka value determined from the graph is 1.9 ×10–4 mol dm–3. This is not the correct value.)
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(1)
(g)     Other than by using a different pH meter, state one way in which the accuracy of the pH readings could be improved.
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(1)
(h)     State why there was little change in the pH value of the mixture when between 8 cm3 and 20 cm3 of alkali were added.
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(1)
(Total 16 marks)

4.	You may find the following electrode potential data helpful when answering this question.
 
Electrode half-equation	Eϴ / V	
Cr2O72–(aq)  + 14H+(aq)  + 6e–  2Cr3+(aq)  + 7H2O(I)	+1.33	
           O2(g)  + 4H+(aq)  + 4e–   2H2O(I)	+1.23	
                           Cr3+(aq)  + e–   Cr2+(aq)	–0.44	
                         Zn2+(aq)  + 2e–   Zn(s)	–0.76	
                         Cr2+(aq)  + 2e–   Cr(s)	–0.91	
(a)	Write equations for any reactions which would take place when an excess of zinc is added to an acidified solution of potassium dichromate (VI) in the absence of air.
In the equations, you should represent the ions in their simplest form, for example Cr3+.
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(2)

(b)     When an aqueous solution containing [Cr(H2O)6]3+ ions is warmed in the presence of Cl– ions, [Cr(H2O)5Cl]2+ ions are formed and the colour of the solution changes.
Name this type of reaction.
Suggest, in terms of electrons, why the colours of the complex ions are different.
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(3)
(c)     The chromium(II) ion [Cr(H2O)6]2+ has different properties from the [Cr(H2O)6]3+ ion.
Use data from the table above to explain why, in an open container, [Cr(H2O)6]2+(aq) ions change into [Cr(H2O)6]3+(aq) ions.
Suggest the identity of the products formed in each case when sodium carbonate solution is added to separate solutions containing [Cr(H2O)6]2+(aq) ions and [Cr(H2O)6]3+(aq) ions.
Explain why the [Cr(H2O)6]3+(aq) ions behave differently from the [Cr(H2O)6]2+(aq) ions.
In your answer to this part of the question, equations are not required.
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(7)
(Total 12 marks)
 
5.   (a)     The iron(II) ions in well-water can be removed by oxidation using potassium manganate(VII) in alkaline solution. A mixture containing solid iron(III) hydroxide and solid manganese(IV) oxide is formed. These solid products can be removed by filtration under reduced pressure.
(i)      Draw a diagram of the apparatus used for this filtration. Do not include the apparatus used to reduce the pressure.

 
 
(2)
(ii)     An equation representing the oxidation reaction is given below.
3Fe2+(aq) + KMnO4(aq) + 5OH–(aq) + 2H2O(I)  3Fe(OH)3(s) + MnO2(s) + K+(aq)
Calculate the mass, in grams, of KMnO4 required to react with the iron(II) ions in 1.00 dm3 of well-water that has an iron(II) concentration of 0.225 mol dm–3. 
Give your answer to the appropriate precision. 
Show your working.
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(3)
(iii)    In practice, a slight excess of potassium manganate(VII) is used to treat the well-water. 
Although this treated water is safe to drink, this excess of potassium manganate(VII) is undesirable. Suggest one reason, other than colour, why the excess is undesirable.
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(1)
(b)     Suggest one reason why the colour of potassium manganate(VII) solution can be a source of error when using a volumetric (graduated) flask to prepare a standard solution.
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(1)
(Total 7 marks)

6.	Which atom has an incomplete sub-shell?
A       Be
B       Ca
C       Ge
D       Zn
(Total 1 mark)

7.	When TiCI4 is reduced with hydrogen under certain conditions, a new compound is produced which contains 68.9% chlorine by mass. Which one of the following could be the formula of the new compound?
A       TiH2Cl2
B       TiCl
C       TiCl2
D       TiCl3
(Total 1 mark)

8.	Which one of the following is the most likely value for the bond angle α shown in the diagram of SF4 below?
 
A       118°
B       101°
C       90°
D       88°
(Total 1 mark)

9.	In which one of the following reactions is the standard enthalpy change equal to the standard enthalpy of formation of lithium fluoride?
A       Li(g) + F(g) → LiF(s)
B       Li+(g) + F−(g) → LiF(s)
C       Li+(aq) + F−(g) → LiF(s)
D       Li(s) + F2(g) → LiF(s)
(Total 1 mark)

10. 

                                             energy
The total area under the distribution curve represents
A       total energy.
B       activation energy.
C       total number of reacting molecules.
D       total number of molecules present.
(Total 1 mark)

11.	A sample of chlorine gas was sealed in a tube, heated and an equilibrium was established.
Cl2(g) ⇌ 2Cl(g)
Which one of the following is not true?
A       The concentration of chlorine atoms remains the same when a catalyst is added to the tube.
B       Increase in temperature causes an increase in the concentration of chlorine atoms.
C       Increase in pressure causes an increase in the concentration of chlorine atoms relative to chlorine molecules.
D       Addition of more chlorine gas to the tube causes an increase in the concentration of chlorine atoms.
(Total 1 mark)

12.	Which of these species is the best reducing agent?
 
 	A	Cl2		
 	B	Cl−		
 	C	I2		
 	D	I−		

(Total 1 mark)

13.	The number of structural isomers of C3H2Cl6 is
A       2
B       3
C       4
D       5
(Total 1 mark)

14.	Which of these substances does not contribute to the greenhouse effect?
 
 	A	Unburned hydrocarbons.		
 	B	Carbon dioxide.		
 	C	Water vapour.		
 	D	Nitrogen.		

(Total 1 mark)

15.	Which statement about ethene is correct?
 
 	A	It has no geometric isomers because there is free rotation around the C=C bond.		
 	B	It reacts with HBr in a nucleophilic addition reaction.		
 	C	It burns in excess oxygen to produce carbon dioxide and water.		
 	D	The C=C bond is twice as strong as the C–C bond in ethane.		

(Total 1 mark)

16.	This question is about a method that can be used to prepare ethylamine.
CH3CH2Br  +  2NH3    CH3CH2NH2  +  NH4Br
 
Which of the curly arrows in the mechanism is not correct?
 
 	A	1		
 	B	2		
 	C	3		
 	D	4		

(Total 1 mark)

17.	Which one of the following best explains why the lattice enthalpy of magnesium chloride is much larger than that of lithium chloride?
A       Magnesium has a greater electronegativity than lithium.
B       Magnesium ions have a greater polarising power than lithium ions.
C       Magnesium ions have a greater ionic radius than lithium ions.
D       Magnesium ions have a greater charge than lithium ions.
(Total 1 mark)

18.	This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:
2SO2(g) + O2(g)  2SO3(g)
Thermodynamic data for the components of this equilibrium are:
 
 	Substance	ΔH / kJ mol−1	S / J K-1 mol-1	
 	SO3(g)	−396	+257	
 	SO2(g)	–297	+248	
 	O2(g)	0	+204	

This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
The standard entropy change for this reaction is
A       −222 J K−1 mol−1
B       −195 J K−1 mol−1
C       −186 J K−1 mol−1
D       +198 J K−1 mol−1
(Total 1 mark)

19.	Addition of which one of the following to 10 cm3 of 1.0 M NaOH would result in the pH being halved?
A       10 cm3 of water
B       100 cm3 of water
C       5 cm3 of 1.0 M HCl
D       10 cm3 of 1.0 M HCl
(Total 1 mark)

20.	Refer to the following reaction
H2(g) + I2(g)  2HI(g)      ΔH = −11 kJ mol−1,      ΔS = +20 J K−1 mol−1
Which one of the following statements is correct?
A       This is a redox reaction.
B       The reaction is not feasible below 298 K
C       At equilibrium, the yield of hydrogen iodide is changed by increasing the pressure.
D       At equilibrium, the yield of hydrogen iodide increases as the temperature is increased.
(Total 1 mark)

21.	In which one of the following reactions is the role of the reagent stated correctly?
 
 	 	Reaction	Role of reagent	
 	A	TiO2 + 2C + 2Cl2 → TiCl4 + 2CO	TiO2 is an oxidising agent	
 	B	HNO3 + H2SO4 → H2NO + HSO	HNO3 is a Brønsted-Lowry acid	
 	C	CH3COCl + AlCl3 → CH3CO+ + AlCl	AlCl3 is a Lewis base	
 	D	2CO + 2NO → 2CO2 + N2	CO is a reducing agent	

(Total 1 mark)

22.	Use the information about the following solutions to answer the question below.
Solution F:    This is a mixture of 1 mol of propanoic acid, 1 mol of methanol and 2 mol of water.
Solution G:    This was originally the same mixture as solution F but it has been left to reach equilibrium.
Compared to the pH of solution F, the pH of solution G will be
A       considerably lower.
B       slightly lower.
C       slightly higher.
D       exactly the same.
(Total 1 mark)

23.	Which one of the following reactions in aqueous solution has the most positive change in entropy?
A       [Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O
B       [Cu(H2O)6]2+ + 4Cl− → [CuCl4]2− + 6H2O
C       [Cu(H2O)6]2+ + EDTA4− → [Cu(EDTA)]2− + 6H2O
D       [Cu(H2O)6]2+ + 2H2NCH2CH2NH2 → [Cu(H2NCH2CH2NH2)2(H2O)2]2+ + 4H2O
(Total 1 mark)

24.	Which one of the following would not reduce an acidified aqueous solution of potassium dichromate(VI)?
A       CH3COOH
B       Zn
C       CH3CHO
D       Fe2+(aq)
(Total 1 mark)

25.	This question is about the following reaction scheme which shows the preparation of polymer P.
 
Polymer P is formed in a two-step reaction from N. The first stage is a neutralisation reaction. The volume, in cm3, of a 0.20 mol dm−3 solution of H2NCH2CH2NH2 required to neutralise 6.8 × 10−3mol of the acid N is
A       17
B       34
C       68
D       136
(Total 1 mark)

26.	The oxidation of ethanedioate (oxalate) ions by manganate(VII) ions can be represented by the half equations:
C2O(aq) → 2CO2(g) + 2e−
MnO (aq) + 8H+(aq) + 5e− → Mn2+(aq) + 4H2O(l)
What volume (in cm3) of 0.02 M KMnO4 is required to oxidise completely a solution containing 0.02 mol of ethanedioate ions?
A       25
B       40
C       250
D       400
(Total 1 mark)

27.	Copper(II) ions can be estimated volumetrically by the addition of an excess of potassium iodide followed by titration of the liberated iodine with sodium thiosulphate solution. The following equations apply:
   2Cu2 + 4I−         →          2CuI + I2
I2 + 2S2         →          S4 + 2I
What volume (in cm3) of 0.1 M Na2S2O3 would be required to react with the iodine produced from 1.249 g of CuSO45H2O (Mr 249.7)?
A       10
B       25
C       50
D       100
(Total 1 mark)

28.	The structural formula of ethyl 2-methylpropanoate is
A       
B       
C       
D       
(Total 1 mark)

29.	Which one of the following reactions will produce an organic compound that has optical isomers?
A       dehydration of butan-2-ol by heating with concentrated sulphuric acid
B       reduction of pentan-3-one by warming with NaBH4
C       addition of Br2 to 3-bromopropene
D       reduction of 2,3-dimethylpent-2-ene with H2 in the presence of a nickel catalyst
(Total 1 mark)

30.	Which one of the following is not a correct general formula for the non-cyclic compounds listed?
A       alcohols CnH2n+2O
B       aldehydes CnH2n+1O
C       esters CnH2nO2
C       primary amines CnH2n+3N
(Total 1 mark)

31.	Which one of the following conversions does not represent a reduction?
A       propene → propane
B       propanal → propan-l-ol
C       propanal → propanoic acid
D       propanone → propane
(Total 1 mark)

32.	Which one of the following can act as an oxidising agent but not as a reducing agent?
A       CH3CHO
B       Fe2+
C       I−
D       MnO
(Total 1 mark)

33. 
 	Summarised directions for recording responses to multiple completion questions	
 	A
(i), (ii) and (iii)
only	B
(i) and (iii) only	C
(ii) and (iv) only	D
(iv) alone	
Isomers of the ester HCOOCH2CH2CH3, include
(i)      ethyl ethanoate
(ii)     methyl propanoate
(iii)    butanoic acid
(iv)    butyl methanoate
(Total 1 mark)

34.	Butan-1-ol was converted into butyl propanoate by reaction with an excess of propanoic acid. In the reaction, 6.0 g of the alcohol gave 7.4 g of the ester. The percentage yield of ester was
A       57
B       70
C       75
D       81
(Total 1 mark)

35.	In which one of the following species is the shape influenced by the presence of one or more lone pairs of electrons?
A       NH
B       NH
C       [CH3NH3]+
D       [Co(NH3)6]2+
(Total 1 mark)