A-LEVEL CHEMISTRY

PAPER 3
PRACTICE PAPER 2

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)     (i)      The addition of aqueous silver nitrate, followed by concentrated aqueous ammonia, can be used to distinguish between separate aqueous solutions of sodium bromide and sodium iodide.
Record what is observed in the table below.
 
 	The addition of AgNO3(aq) 	followed by 	the addition of
concentrated NH3(aq)	
Observation with
NaBr(aq)	 	 	
Observation with
NaI(aq)	 	 	
					
(ii)     Explain why it is not possible to distinguish between separate solutions of sodium nitrate and sodium fluoride by the addition of silver nitrate solution.
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(5)
(b)     Aqueous silver nitrate can be used to distinguish between chloroethanoic acid and ethanoyl chloride.
(i)      Draw the structure of ethanoyl chloride. Predict what, if anything, you would observe when ethanoyl chloride is added to aqueous silver nitrate.
Structure of ethanoyl chloride

  
 
Observation ........................................................................................
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(ii)     Draw the structure of chloroethanoic acid. Predict what, if anything, you would observe when chloroethanoic acid is added to aqueous silver nitrate.
Structure of chloroethanoic acid

  
Observation ........................................................................................
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(4)

(d)     (i)      Tollens’ reagent is formed by the addition of aqueous ammonia to aqueous silver nitrate. Identify the silver-containing complex present in Tollens’ reagent and state its shape.
Silver-containing complex ...................................................................
Shape…...............................................................................................
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(ii)     Draw the structure of methanoic acid. By reference to this structure, suggest why a silver mirror is formed when this acid reacts with Tollens’ reagent.
Structure .............................................................................................
Explanation….......................................................................................
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(iii)     Deduce the identity of a carbon-containing species formed when methanoic acid reacts with Tollens’ reagent.
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(5)
(Total 14 marks)
 
2.	In an experiment to determine the acid dissociation constant (Ka) of a weak acid, 25.0 cm3 of an approximately 0.1 mol dm–3 solution of this acid were titrated with a 0.10 mol dm–3 solution of sodium hydroxide.
The pH was measured at intervals and recorded. The table below shows the results.
 
 	Volume of NaOH / cm3	0.0	1.0	2.0	3.0	4.0	5.0	10.0	15.0	
 	pH	5.1	7.8	8.1	8.7	8.4	8.5	8.9	9.3	

 	Volume of NaOH / cm3	20.0	22.0	23.0	24.0	25.0	26.0	27.0	28.0	
 	pH	9.7	10.0	10.2	11.0	11.3	11.4	11.5	11.6	
 
(a)     On the grid below, plot the values from the table above on a graph of pH (y-axis) against volume of NaOH. 
You should start your y-axis at pH 4.0. 
Draw a curve that represents the curve of best fit through these points. Ignore any anomalous points.
 
(4)
(b)     Deduce the volume of the sodium hydroxide solution that would have been added at the half-neutralisation point of this experiment. This is the point where half the amount of the weak acid has been neutralised.
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(1)

(c)     When half of the weak acid has been neutralised, the pH of the mixture at this point is equal to the pKa of the weak acid.
Use your answer to part (b) and your graph to determine the pKa of the weak acid and, hence, its Ka value.
pKa ...................................................................................................................
Ka .....................................................................................................................
(2)
(d)    State the pH value for the anomalous point on your graph. 
Suggest one reason for this anomaly. Assume that the reading on the pH meter is correct.
pH ..................................................................................................................
Reason for anomaly .......................................................................................
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(1)
(e)     Suggest how the experimental procedure could be slightly modified in order to give a more reliable value for the end-point.
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(1)
(Total 9 marks)

3.	Iron(II) ethanedioate is another insoluble solid used as a pigment in paints and glass. It occurs as a dihydrate (FeC2O4.2H2O). One procedure used for the preparation of iron(II) ethanedioate is outlined below.
Procedure 
A 6.95 g sample of hydrated iron(II) sulfate (FeSO4.7H2O) was added to 100 cm3 of water in a beaker and stirred until all of the solid dissolved. A 150 cm3 volume of 0.20 mol dm–3 sodium ethanedioate solution was added to the beaker. The mixture was stirred until precipitation was complete. After filtration, 3.31 g of the dihydrate (FeC2O4.2H2O) were collected.
(a)     Write an equation for the reaction between iron(II) sulfate and sodium ethanedioate.
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(1)
(b)     Calculate the amount, in moles, of FeSO4.7H2O in 6.95 g of hydrated iron(II) sulfate. Show your working.
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 (2)

(c)     Calculate the amount, in moles, of sodium ethanedioate in 150 cm3 of 0.20 mol dm–3 sodium ethanedioate solution.
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(1)
(d)     Calculate the percentage yield of iron(II) ethanedioate dihydrate (Mr = 179.8) formed in this reaction. 
Give your answer to the appropriate precision. Show your working.
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(2)
(e)     In this experiment, no side reactions take place, the reagents are pure and the reaction goes to completion.
Suggest one reason why the yield of iron(II) ethanedioate dihydrate in this experiment is less than 100%.
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(1)
(f)      When dissolved in dilute sulfuric acid, the number of moles of ethanedioate ions in a pigment can be determined by titration with acidified potassium manganate(VII).
Explain why the titration of a sample of iron(II) ethanedioate would require a different amount of potassium manganate(VII) than a titration of an equimolar amount of copper(II) ethanedioate.
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(2)
(Total 9 marks)

4.   (a)     Because of the toxic nature of the copper(II) ion, a wide range of alternative anti-fungal drugs has been developed for use in agriculture. One example is Zineb.
 
(i)      The negative ion in Zineb could act as a bidentate ligand.
On the structure above, draw a ring around each of two atoms that could provide the lone pairs of electrons when this ion acts as a bidentate ligand.
(1)
(ii)     Calculate the Mr of Zineb. Give your answer to the appropriate precision.
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(1)
(iii)    Name the functional group formed at each end of the negative ion when all the sulfur atoms in the structure of Zineb are replaced by oxygen atoms.
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(1)
(b)     Zineb has been investigated for harmful effects. Generally, Zineb has been found to be safe to use in agriculture. It is only slightly soluble in water and is sprayed onto plants. A breakdown product of Zineb is ethylene thiourea (ETU), which is very soluble in water. The structure of ETU is shown below.
 
Determine the percentage, by mass, of sulfur in ETU (Mr = 102.1).
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(1)

(c)     Chromatography is a technique used to show the presence of a small amount of ETU in Zineb.
Outline how this technique is used to separate and identify ETU from a sample of Zineb powder.
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(4)
(Total 8 marks)

5.          When anhydrous iron(III) chloride is added to water the following reaction occurs.
 [Fe(H2O)6]3+ + H2O → [Fe(H2O)5(OH)]2+ + H3O+
(a)	State the type of acidity shown by [Fe(H2O)6]3+ in this reaction. Explain your answer.
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(2)
(b)     Explain why the pH of a solution of iron(II) chloride is higher than that of a solution of iron(III) chloride of the same concentration.
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(2)

(c)	Transition metals have variable oxidation states. This is an important factor in their ability to act as heterogeneous and homogeneous catalysts.
(i)      Vanadium(V) oxide acts as a heterogeneous catalyst in the Contact Process. Write equations to show the role of vanadium(V) oxide in this process.
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(ii)     In aqueous solution, Fe2+ ions act as a homogeneous catalyst in the reaction between I– and S2O82– ions. Give one reason why the reaction is slow in the absence of a catalyst. Write equations to show how Fe2+ ions act as a catalyst for this reaction.
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(7)
(Total 11 marks)
 
6.      (a)     Methylamine is a weak Brønsted-Lowry base and can be used in aqueous solution with one other substance to prepare a basic buffer.
(i)      Explain the term Brønsted-Lowry base and write an equation for the reaction of methylamine with water to produce an alkaline solution.
Brønsted-Lowry base ..........................................................................
Equation ..............................................................................................
(ii)     Suggest a substance that could be added to aqueous methylamine to produce a basic buffer.
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(iii)     Explain how the buffer solution in part (a)(ii) is able to resist a change in pH when a small amount of sodium hydroxide is added.
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(5)

(b)     Explain why methylamine is a stronger base than ammonia.
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(2)
(c)     A cation is formed when methylamine reacts with a large excess of bromoethane. Name the mechanism involved in the reaction and draw the structure of the cation formed.
Name of mechanism ....................................................................................
Structure

 
(2)
(Total 9 marks)
 
7.	Which one of the following ionisations requires less energy than the first ionisation energy of oxygen?
A       S(g) → S+(g) + e−
B       O+(g) → O2+(g) + e−
C       N(g) → N+(g) + e−
D       F(g) → F+(g) + e−
(Total 1 mark)

8.	Which of these samples of gas contains the largest number of molecules?
The gas constant R = 8.31 J K–1 mol–1.
 
 	A	5.0 × 10–4 m3 at 1.0 × 106 Pa and 300 K		
 	B	4.0 × 10–3 m3 at 2.0 × 105 Pa and 400 K		
 	C	3.0 × 101 dm3 at 3.0 × 104 Pa and 500 K		
 	D	2.0 × 102 dm3 at 4.0 × 103 Pa and 600 K		

(Total 1 mark)

9.	Which one of the following has a shape which is not influenced by a lone pair of electrons?
A       CH3OH
B       H2F+
C       BF3
D       NF3
(Total 1 mark)

10.	Given the following data
C(s) + 2H2(g) → CH4(g)                       ∆H = −75 kJ mol−1
  H2(g) → 2H(g)                           ∆H = +436 kJ mol−1
which one of the following is the enthalpy change, in kJ mol−1, of the reaction below?
CH4(g) → C(s) + 4H(g)
A       −947
B       +511
C       +797
D       +947
(Total 1 mark)

11.	This question is about the Maxwell–Boltzmann distribution of molecular energies in a sample of a gas shown in the figure below.
 
Which letter best represents the mean energy of the molecules?
 
 	A		
 	B		
 	C		
 	D		

(Total 1 mark)

12.	The equilibrium constant, Kc, for a reaction which leads to ozone (O3) formation is

More ozone is formed as the temperature rises. Which one of the following is true at equilibrium?
A       When ozone molecules collide with nitrogen they may form nitrogen monoxide.
B       The enthalpy change for the reaction has a negative sign.
C       Less ozone is formed at high pressure.
D       At a fixed temperature, the magnitude of Kc increases as the concentration of NO decreases.
(Total 1 mark)

13.	Which of the following shows chlorine in its correct oxidation states in the compounds shown?
 
 	 	HCl	KClO3	HClO	 	
 	A	−1	+3	+1		
 	B	+1	−5	−1		
 	C	−1	+5	+1		
 	D	+1	+5	−1		

(Total 1 mark)

14.	Which one of the following is not a correct trend down Group VII?
A       The first ionisation energy of the atom decreases.
B       The oxidising power of the element increases.
C       The electronegativity of the atom decreases.
D       The boiling point of the element increases.
(Total 1 mark)

15.	This question concerns the preparation of the plastic poly(methyl 2-methylpropenoate) (Perspex), starting from propanone.
 
Which one of the following is not a structural isomer of Compound M?
A        
B        
C        
D        
(Total 1 mark)

16.	Which one of the following is least likely to occur in the reaction between methane and chlorine?
A       CH4 + Cl• → CH3• + HCl
B       CH3• + HCl → CH3Cl + H•
C       CH3• + Cl2 → CH3Cl + Cl•
D       CH3Cl + Cl• → CH2Cl• + HCl
(Total 1 mark)

17.	Which statement about E-1,2-dichloroethene is correct?
 
 	A	It has the same boiling point as Z-1,2-dichloroethene.		
 	B	It forms a polymer with the same repeating unit
as Z-1,2-dichloroethene.		
 	C	It has the same IR spectrum as Z-1,2-dichloroethene
in the range 400–1500 cm−1.		
 	D	It has a molecular ion peak different from that of
Z-1,2-dichloroethene in its mass spectrum.		

(Total 1 mark)

18.	Using the information below, answer this question.
Fe2O3(s) + 3H2(g) → 2Fe(s) + 3H2O(g)   ΔH= +96 kJ mol−1,  ΔS = +138 J K−1 mol−1
 
 	 	Fe2O3(s)	H2(g)	Fe(s)	
 	ΔH / kJ mol−1	−822.0	       0	        0	
 	ΔS / J K−1 mol−1	    90.0	131.0	    27.0	
The standard entropy value for steam is
A       +332 J Kࢤ1 mol−1
B       +189 J Kࢤ1 mol−1
C       +145 J Kࢤ1 mol−1
D       +85 J Kࢤ1 mol−1
(Total 1 mark)

19.	In which one of the following reactions is there a decrease in entropy?
A       [Fe(H2O)6]3+(aq) + 3C2O (aq) → [Fe(C2O4)3]3−(aq) + 6H2O(l)
B       [Cu(H2O)6]2+(aq) + EDTA4−(aq) → [Cu(EDTA)]2−(aq) + 6H2O(l)
C       [CoCl4]2−(aq) + 6H2O(l) → [Co(H2O)6]2+(aq) + 4Cl− (aq)
D       Na2CO3(s) + 2H+(aq) → 2Na+(aq) + CO2(g) + H2O(l)
(Total 1 mark)

20.	The equation and rate law for the reaction of substance P with substance Q are given below.
2P + Q → R + S
        rate = k[P]2[H+]
Under which one of the following conditions, all at the same temperature, would the rate of reaction be slowest?
[P] / mol dm−3         pH
A               0.1                    0
B                1                     2
C                3                     3
D               10                    4
(Total 1 mark)

21.	This question refers to the reaction sequence below.
 
HCN is a weak acid with a pKa value of 9.40. If a 0.010 mol dm−3 solution of HCN was used in the first step, the concentration of cyanide ions, in mol dm−3, would be
A       2.0 × 10−6
B       6.4 × 10−5
C       2.0 × 10−5
D       3.1 × 10−1
(Total 1 mark)

22.	Which one of the following statements is true?
A       A blue solution containing the ion [CoCl4]2− turns pink when added to an excess of water.
B       A purple solution is formed when chlorine is bubbled into aqueous sodium bromide.
C       A yellow precipitate is formed when aqueous silver nitrate is added to aqueous sodium chloride.
D       A green solution containing the ion [CuCl4]2− turns blue when added to an excess of concentrated hydrochloric acid.
(Total 1 mark)

23.	Aqueous C2O ions react with MnO ions in acidic solution according to the equation
5 C2O + 2MnO + 16H+ → 2Mn2+ + 10CO2 + 8H2O
Under the same conditions Fe2+ ions also react with MnO ions. How many moles of MnO ions are required to react exactly with one mole of Fe(C2O4).2H2O?
A       0.4
B       0.6
C       2.5
D       7.5
(Total 1 mark)

24.	In which one of the following reactions does hydrogen not act as a reducing agent?
A       H2 + Ca → CaH2
B       2H2 + O2 → 2H2O
C       H2 + CH2=CH2 → CH3CH3
C       2H2 + CH3COCH3 → CH3CH2CH3 + H2O
(Total 1 mark)

25.	The percentage of copper in a copper(II) salt can be determined by using a thiosulphate titration. 0.305 g of a copper(II) salt was dissolved in water and added to an excess of potassium iodide solution, liberating iodine according to the following equation:
2Cu2+(aq) + 4I−(aq) → 2CuI(s) + I2(aq)
The iodine liberated required 24.5 cm3 of a 0.100 mol dm−3 solution of sodium thiosulphate:
2S2O(aq) + I2(aq) → 2I−(aq) + S4O(aq)
The percentage of copper, by mass, in the copper(II) salt is
A       64.2
B       51.0
C       48.4
D       25.5
(Total 1 mark)

26.	This question is about the reaction between propanone and an excess of ethane-1,2-diol, the equation for which is given below.
 
In a typical procedure, a mixture of 1.00 g of propanone, 5.00 g of ethane-1,2-diol and 0.100 g of benzenesulphonic acid, C6H5SO3H, is heated under reflux in an inert solvent. Benzenesulphonic acid is a strong acid.
If 0.100 g of the strong monoprotic acid, benzenesulphonic acid, was dissolved in 100 cm3 of water, the pH of the solution would be
A       0.20
B       1.20
C       2.20
D       3.20
(Total 1 mark)

27.	Which compound is formed by the reaction of ethane-1,2-diol with an acid?
A        
B        
C        
 
D        CH3CH2 — O — CH2CH2OH
(Total 1 mark)

28.	In which of the following is a curly arrow used incorrectly?
A       
B       
C       
D       
(Total 1 mark)

29.	The compound lithium tetrahydridoaluminate(III), LiAlH4, is a useful reducing agent. It behaves in a similar fashion to NaBH4. Carbonyl compounds and carboxylic acids are reduced to alcohols. However, LiAlH4 also reduces water in a violent reaction so that it must be used in an organic solvent.
Which one of the following concerning the violent reaction between LiAlH4 and water is false?
A       A gas is produced.
B       The activation energy for the reaction is relatively high.
C       The reaction has a negative free-energy change.
D       Aqueous lithium ions are formed.
(Total 1 mark)

30.	Which one of the following types of reaction is not involved in the above sequence?
CH3CH2CH3   (CH3)2CHCl   (CH3)2CHCN
                                                                                   
     (CH3)2CHCH2NHCOCH3   (CH3)2CHCH2NH2
A       halogenation
B       acylation
C       reduction
D       oxidation
(Total 1 mark)

31.	Which one of the following would not react with aqueous silver nitrate to produce a precipitate that is soluble in concentrated aqueous ammonia?
A       CaBr2
B       [COCI4]2−
C       (CH3)4N+I−
D       CH3COCl
(Total 1 mark)

32.	Propanoic acid reacts with methanol in the presence of a small amount of concentrated sulphuric acid. The empirical formula of the ester formed is
A       CH2O
B       C2H6O2
C       C2H4O2
D       C2H4O
(Total 1 mark)

33.	Which one of the following reactions does not involve donation of an electron pair?
A       H+ + CH3NH2 → CH3NH
B       AlCl3 + Cl− → A1C1
C       CH3Cl + CN− → CH3CN + Cl−
D        Cl2 + I− → Cl− +  I2
(Total 1 mark)

34.	Hydrolysis of the ester, CH3COOCH2CH2CH3, produces ethanoic acid. In an experiment, 2.04 g of the ester was used and 0.90 g of ethanoic acid was produced. The percentage yield of ethanoic acid was:
A       44
B       59
C       75
D       90
(Total 1 mark)

35.	CH2O is the empirical formula of
A       methanol
B       methyl methanoate
C       ethane-1,2-diol
D       butanal
(Total 1 mark)

36.	How many peaks will be observed in the low-resolution proton n.m.r. spectrum of (CH3)2CHCOO(CH2)3CH3?
A       4
B       5
C       6
D       7
(Total 1 mark)