AS & A Level Chemistry - 9701 Paper 2 2023 Summer Zone 3

Copper is used in electrical equipment. It has a melting point of 1085°C.

(a) (i) Identify the lattice structure of copper.
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(ii) Draw a labelled diagram to show the bonding present in copper. [1]

(b) The relative isotopic masses and natural abundances of the two isotopes in a sample of copper are shown in Table 1.1.

[Table 1.1]
| isotope | relative isotopic mass | % abundance |
|---------|-----------------------|-------------|
| $^{63}\text{Cu}$ | 62.930 | 69.15 |
| $^{65}\text{Cu}$ | 64.928 | 30.85 |

(i) Define the unified atomic mass unit.
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(ii) Define relative atomic mass, $A_{r}$, in terms of the unified atomic mass unit.
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(iii) Calculate the relative atomic mass, $A_{r}$, of copper in this sample using the data in Table 1.1.
Show your working.
$A_{r}$ = .................................. [1]

(c) The mass spectrum of a sample of pure copper is shown in Fig. 1.1.

Fig. 1.1
Identify the ion with an abundance of 23% in the sample.
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(d) When KI(aq) is added to CuSO$_{4}$(aq) the blue-coloured solution turns brown and a white precipitate of CuI(s) is seen.
The reaction between copper ions and iodide forms only two products.

(i) Complete the equation for this reaction.
............Cu$^{2+}$ + ...........I$^{-}$ → ............CuI + ..................................
[1]

(ii) Identify the oxidising agent in this reaction. Explain your answer in terms of electron transfer.
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(iii) State the full electronic configuration of Cu$^{2+}$.
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(a) The reaction of pure aluminium is only observed if the aluminium oxide layer is removed first. When pure aluminium is added to cold water, bubbles of gas are seen.
(i) State one property of aluminium oxide that explains why an aluminium object does not react with cold water until the aluminium oxide layer is removed.
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(ii) Write an equation, with state symbols, for the reaction of aluminium oxide with an excess of NaOH(aq).
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(iii) Name one other Period 3 element that also produces bubbles of gas when added to cold water.
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(b) Aluminium nitrate is a white soluble salt. On heating aluminium nitrate, thermal decomposition occurs and a brown gas is seen.
State the formula of the salt of another element in Period 3 which also decomposes on heating to produce a brown gas.
........................................................................................................................................... [1]

(c) Aluminium chloride and phosphorus chloride are both white solids.
(i) State the maximum oxidation number of aluminium and of phosphorus in these solid chloride salts.
maximum oxidation number of aluminium ..............................................
maximum oxidation number of phosphorus .............................................. [1]
(ii) State why the maximum oxidation number of aluminium is different from that of phosphorus.
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(iii) Write an equation for the reaction of solid phosphorus chloride and excess water.
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(iv) Name the type of reaction that occurs when aluminium chloride is added to water.
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(v) Explain why the solution produced after aluminium chloride is added to water has a pH of 1–2.
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A neutralisation reaction occurs when NaOH(aq) is added to H_2SO_4(aq).
equation 1 $2\text{NaOH(aq)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{Na}_2\text{SO}_4\text{(aq)} + 2\text{H}_2\text{O(l)}$
(a) Define enthalpy change of neutralisation, $\Delta H_{\text{neut}}$.
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(b) In an experiment, 50.0 $\text{cm}^3$ of 2.00 $\text{mol dm}^{-3}$ NaOH(aq) is added to 60.0 $\text{cm}^3$ of 1.00 $\text{mol dm}^{-3}$ H_2SO_4(aq) in a polystyrene cup and stirred. Both solutions have a temperature of 21.4 $^{\circ}$C before mixing. The maximum temperature of the mixture is measured.
(i) Use equation 1 to calculate the amount, in mol, of H_2SO_4(aq) that is neutralised in the experiment.
amount of H_2SO_4 neutralised = ................................. mol [1]
(ii) Calculate the theoretical maximum temperature of the mixture in this experiment.
Assume that:
\begin{itemize} \item enthalpy change of neutralisation, $\Delta H_{\text{neut}}$, of NaOH(aq) and H_2SO_4(aq) is $-57.1 \text{kJ mol}^{-1}$ \item full dissociation of H_2SO_4(aq) occurs \item the specific heat capacity of the final solution is $4.18 \text{J g}^{-1} \text{K}^{-1}$ \item 1.00 $\text{cm}^3$ of the final solution has a mass of 1.00 g \item there is no heat loss to the surroundings \item the experiment takes place at constant pressure. \end{itemize}
Show your working.
theoretical maximum temperature = ............................. $^{\circ}$C [3]

(c) The enthalpy change of neutralisation of CH_3COOH(aq) and NaOH(aq) is $-55.2 \text{kJ mol}^{-1}$.
(i) Complete the equation for the reaction.
.........CH_3COOH + .........NaOH $\rightarrow$ ........................................................................... [1]
(ii) Values for the enthalpy change of neutralisation, $\Delta H_{\text{neut}}$, are shown in Table 3.1.
[Table_1]
Suggest why the value for $\Delta H_{\text{neut}}$ of the weak acid, CH_3COOH, reacting with NaOH is different to the value obtained using the strong acid, HCl. Assume that the values are determined under the same conditions.
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(a) Hydrogen chloride gas is made in the laboratory by adding concentrated sulfuric acid to potassium chloride.
(i) Construct an equation for this reaction.
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(ii) Explain why hydrogen iodide is not prepared by adding concentrated sulfuric acid to sodium iodide.
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(b) A sample of HI(g) is added to a 2.00 dm³ sealed vessel at 764 K and allowed to reach equilibrium.
reaction 1 ↔ 2HI(g) ⇌ H₂(g) + I₂(g)   K_c = 0.0217 at 764 K
At equilibrium the mixture contains 1.70 mol of HI(g).
(i) State one difference in the appearance of the initial reaction mixture compared to the mixture at equilibrium.
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(ii) Deduce the expression for equilibrium constant K_c for reaction 1.
K_c = ............................................................................................... [1]
(iii) Calculate the concentration of I₂ present in the reaction mixture at equilibrium. Show your working.
concentration of I₂ = ................................... mol dm^-3 [3]

(c) The experiment is repeated at 500 K. The value of K_c under these conditions is 0.00625.
(i) Describe the difference in the composition of the equilibrium mixture at 500 K compared to 764 K.
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(ii) Use Le Chatelier’s principle to deduce whether the decomposition of HI(g) is endothermic or exothermic. Explain your answer.
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Y is formed from X in a single-step reaction, as shown in Fig. 5.1.

(a) Deduce the empirical formula of Y.
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(b) The formation of Y from X requires the addition of a suitable reducing agent.
(i) Construct an equation using molecular formulae and [H] for the reaction in Fig. 5.1. Use [H] to represent one atom of hydrogen from the reducing agent.
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(ii) Identify a suitable non-gaseous reducing agent for the formation of Y from X.
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(c) Complete Table 5.1 to show the number of sp^2 and sp^3 hybridised carbon atoms in a molecule of X.
[Table_1]
[2]
(d) Complete Table 5.2 with the expected observations that occur when the reagents shown are added to separate solutions of X and Y. Do not refer to temperature changes in your answer.
[Table_2]
[3]

Compound W, CH$_2$=CHCN, is used to make an addition polymer which is present in carbon fibres.
(a) Draw one repeat unit of the addition polymer of W.
[1]
(b) CH$_3$CHO is used in a two-step synthetic route to form W, as shown in Fig. 6.1.
In step 1, CH$_3$CHO is heated with HCN in the presence of KCN.

(i) Name the mechanism for the reaction in step 1 in Fig. 6.1.
[1]
(ii) Complete Fig. 6.2 to show the mechanism for the reaction in step 1.
Include all products, charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.

[3]
(iii) Suggest a suitable reagent and conditions for step 2 in Fig. 6.1.
[1]
(iv) Fig. 6.3 shows the infrared spectrum of W, CH$_2$=CHCN.

Use Table 6.1 to identify the bonds responsible for the absorptions marked S and T on Fig. 6.3.
S .................................
T .................................
[1]
(c) Molecules of W, CH$_2$=CHCN, do not show stereoisomerism.
(i) Describe stereoisomerism.
[1]
(ii) Describe the two essential features of an alkene molecule that cause it to show geometrical stereoisomerism.
[2]
(d) Molecules of CH$_3$CH(OH)CN exist as a pair of optical isomers.
Draw three-dimensional diagrams in the boxes to show the optical isomers of CH$_3$CH(OH)CN.

[1]
(e) Propanenitrile is heated with hydrogen gas and a platinum catalyst. The only product is propylamine.
Construct an equation for this reaction.
[1]
(f) Propylamine can also be formed in a two-step synthesis from propan-1-ol, as shown in Fig. 6.4.

(i) Name the type of reaction in step 1 in Fig. 6.4.
[1]
(ii) Identify the reagent and conditions for step 2 in Fig. 6.4.
[2]