科目：化学 Chemistry (9701)
年份：2022 冬季
试卷：Paper 42
总页数：21
章节：19 Lattice energy, 20 Electrochemistry, 21 Further aspects of equilibria, 22 Reaction kinetics, 23 Entropy and Gibbs free energy, 24 Transition elements, 25 Benzene and its compounds, 26 Carboxylic acids and their derivatives, 27 Organic nitrogen compounds, 30 Analytical chemistry
1 Calcium chloride, CaCl$_2$, is an ionic solid.
The values of some energy changes are shown in Table 1.1.
Table 1.1
| energy change | value/kJ mol$^{-1}$ |
| :--- | :--- |
| lattice energy, $\Delta H_{\text{latt}}^{\circ}$, CaCl$_2$(s) | $-2237$ |
| standard enthalpy change of atomisation of calcium | +193 |
| first ionisation energy of calcium | +590 |
| second ionisation energy of calcium | +1150 |
| standard enthalpy change of atomisations of chlorine | +121 |
| first electron affinity of chlorine | $-364$ |
(a) Define lattice energy.
[1]
(b) Use the data in Table 1.1 to calculate the standard enthalpy change of formation, $\Delta H_{\text{f}}^{\circ}$, of calcium chloride. It may be helpful to draw an energy cycle. Show all your working.
$$\Delta H_{\text{f}}^{\circs}(\text{CaC(c) Three possible values for the first electron affinity of bromine are shown in Table 1.2. One of them is correct.
Place a tick by the correct value. Explain your choice.
Table 1.2
| possible values | place one tick ($\surd$) in this column |
| :--- | :--- |
| $-342 \text{ kJ mol}^{-1}$ | |
| $-364 \text{ kJ mol}^{-1}$, | |
| $-386 \text{ kJ mol}^{-1}$$ | |
explanation ... [1]
(d) The enthalpy change of hydration of the chloride ion can be calculated using the lattice energy of calcium chloride and the data shown in Table 1.3.
Table 1.3
| energy change | value / kJ mol$^{-1}$ |
| :--- | :--- |
| standard enthalpy change of solution of CaCl$_2$(s) | $-83$ |
| standard enthalpy change of hydration of Ca$^{2+}$(g) | $-1650$ |
(i) Define the following terms.
enthalpy change of solut(e) Calcium fluoride, CaF$_2$(s), can be synthesised directly from its elements.
The value of $\Delta H_f^\circ(\text{CaF}_2(s))$ is $-1214 \text{ kJ mol}^{-1}$.
(i) Predict the sign of the entropy change, $\Delta S^\circ$, for this synthesis. Explain your answer.
The sign of the entropy change is ..... .
explanation ..... [1]
(ii) Use the value of $\Delta H_f^\circ(CaF_2(s))$ given in (e) and your answer to (e)(i) to predict how the feasibility for this synthesis will change with increasing temperature.
[Total: 11]2 (a) Nitrogen monoxide, NO, reacts with ozone, O$_3$.
$$\text{NO(g)} + \text{O}_3(\text{g}) \rightarrow \text{NO}_2(\text{g}) + \text{O}_2(\text{g})$$
This reaction is first order with respect to both NO and O$_3$. At 298 K, the rate constant $k = 11500 \text{ mol}^{-1} \text{ dm}^3\text{ s}^{-1}$.
(i) Complete the rate equation for this reaction.
$$\text{rate} = ...$$ [1]
(ii) A reaction is carried out in which the initial concentrations of NO and O$_3$ are both $1.20 \times 10^{-6} \text{ mol dm}^{-3}$.
Calculate the initial rate of the reaction. State its units.
$$\text{rate of reaction} = ... \quad \text{units} = ...$$ [2]
(iii) The reaction described in (a)(ii) is monitored over a period of time.
Predict whether or not the graph of [NO] against time, under these conditions, (ii) Sketch a graph, on the axes below, of $[N_2O]$ against time for this reaction. ![Graph showing $[N_2O]$ vs. time](image) (iii) Platinum behaves as a heterogeneous catalyst in this reaction. Describe the mode of action of a heterogeneous catalyst. [3] (iv) Suggest a reason why this reaction has zero order kinetics when the amount of nitrous oxide is large and the amount of platinum is small. [1] [Total: 10]
Question 3 starts on the next page.
3 Data should be selected from Table 3.1 in order to answer some parts of this question.
Table 3.1
| electrode reaction | $E^\circ$/V |
| :--- | :--- |
| $\text{Mg}^{2+} + 2\text{e}^- \rightleftharpoons \text{Mg}$ | $-2.38$ |
| $\text{Mn}^{2+} + 2\text{ e}^- \rightleftharpoons\text{Mn}$ | $-1.18$ |
| $\text{Mn}^3^+ + \text{e}^- \rightlefthARMS^{2+}$ | $+1.49$ |
| $\text{MnO}_2 + 4\text{H}^+ + 2\text{e}^- \Rightarrow \text{Mn}^{2+} + \text{2H}_2\text{O}$ | $+1.23$ |
| $\text{MnO}_{4}^- + \text{e}^- \Rightarrow \text {MnO}_{4}^{2-}$ | $+0.56$ |
| $\text{MnO_{4}^-} + 4\text{H}^+ +3\text{e}^- \Rightarrow \mathrm{MnO}_2 + 2\mathrm{H}_2\text{O}$ | $+\mathrm{1.67}$ |
| $\text{MnO}_{{4}}^{-} + 8\text{H}^+ +5\text{e}^- \Rightarrow \mathbb{Mn}^{2+} + 4\mathbb{H}_2\text{O}$ | $\mathrm{+1.52}$ |
(a(iv) Calculate the standard cell potential, $E^\circ_{\text{cell}}$, of this cell.
$$E^\circ_{\text{cell}} = \dots\dots\dots\dots\ V$$ [1]
(v) Construct an equation for the cell reaction.
[1]
(vi) Predict how the cell reaction will change, if at all, when the solution in the Mg$^{2+}$/Mg half-cell is diluted by the addition of a large volume of water. Explain your answer.
[1]
(b) A molten magnesium salt is electrolysed for 15.0 minutes by a constant current.
$$4.75 \times 10^{22} \text{ magnesium atoms are produced at the cathode}$$
Calculate the value of the current used.
current = $\dots\dots\dots\ldots\ A$ [2]
[Total: 11]4 (a) The value of the solubility product, $K_{\text{sp}}$, of iron(III) hydroxide, Fe(OH)$_3$, is given by the following expression.
$$K_{\text{sp}} = [\text{Fe}^{3+}][\text{OH}^-]^3 = 2.0 \times 10^{-39} \text{mol}^4 \text{dm}^{-12}$$
(i) Calculate the solubility of Fe(OH)$_3$ in water.
solubility = ..... mol dm$^{-3}$ [1]
(ii) Calculate the solubility of Fe(ОН)$_3$ in 0.010 mol dm$^{-3}$ barium hydroxide, Ba(OH)$_2$(aq).
solubility = ..... mol dm$-3$ [2]
(iii) Fe(OH)$_3$ is less soluble in Ba(OH)$_2$(aq) than it is in pure water.
Name this effect.
[1]
(b) The numerical value of the $K_a$ of HBrO is $2.00 \times 10^{-9}$.
X is a solution of HBrO which contains $4.00 \times 10^{-3}$ mol of HBrO in $100\text{cm}^3$ of solution. In this solution the following equilibrium is establ(iii) Calculate the pH of solution X. Show all your working.
$$\text{pH} = \dots\dots\dots\dots\ldots\ldots\ldots\ldotfill [2]$$
(iv) A solution containing $2.00 \times 10^{-3}$ mol of NaOH is added to solution X. A buffer solution is formed.
Calculate the pH of this buffer solution.
$$\text{pH} = ...\dots\dots\dots...\ldots\ldotfill [1]$$
[Total: 9]5 Copper is a transition element. It forms a wide variety of compounds.
(a) Define transition element.
(b) An aqueous solution of copper(II) sulfate, CuSO$_4$, contains $[\text{Cu(H}_2\text{O})_6]^{2+}$ complex ions. If an excess of concentrated hydrochloric acid is added to this solution a ligand exchange reaction occurs and $[\text{CuCl}_4]^{2-}$ complex ions are formed.
(i) Complete Table 5.1 to state the geometry, the coordination number of copper, and one bond angle in each of the two complex ions.
| complex ion | geometry | coordination number | bond angle |
| :--- | :---: | :---: | :---: |
| $[\text{Cu(H}_2\text {O})_6]^{2+}$ | | | |
| $[\text{CuC l}_4]^{2-}$ | | | |
(ii) In an isolated $\text{Cu}^{2+}$ ion the d-orbitals are all degenerate. In a complex ion such as $[\text{Cu((ii) There are three stereoisomers with the formula $[\text{Cu}(\text{C}_2\text{O}_4)_2(\text{H}_2\text{O})_2]^{2-}$.
Complete the three-dimensional diagrams to show these three stereoisomers.
[2]
(iii) Use your answer to (c)(ii) to answer this question.
Stereoisomers 1, 2 and 3 show two different types of isomerism.
Name these two types of isomerism.
For each type of isomerism identify the pair of stereoisomers that demonstrate this isomerism.
| type of isomerism | pair of stereoisomers |
| :--- | :--- |
| | and |
| | and |(d) A solution contains 3.70 g of Na$_2$[Cu(C$_2$O$_4$)$_2$(H$_2$O)$_2$] dissolved in 100 cm$^3$ of solution. A 25.0 cm$^3$ sample of this solution is warmed and then oxidised by 0.0100 mol dm$^{-3}$ acidified potassium manganate(VII).
The equation for the redox reaction is shown.
$$5\text{C}_2\text{O}_4^{2-} + 2\text{MnO}_4^- + 16\text{H}^+ \rightarrow 10\text{CO}_2 + 2\text{Mn}^{2+} + 8\text{H}_2\text{O}$$
Calculate the minimum volume of 0.0100 mol dM$^{-3}$ acidified potassium mangANATE(VII) needed to oxidise all of the ethanedioate ions, C$_2\text{O}_4^{2-}$, in the 25.0 cm$^3$-sample. Show all your working.
$$\text{[M}_r: \text{Na}_2[\text{Cu(C}_2\text{O}_4)_2(\text{H}_2\text{O})_2], 321.5]$$
minimum volume = ..... cm$^3$ [3]
(e) Copper(II) nitrate, Cu(NO$_3$)$_2$, and barium ni6 An aqueous solution of cobalt(II) chloride is a pink colour due to the presence of $[\text{Co}(\text{H}_2\text{O})_6]^{2+}$ complex ions.
(a) (i) Complete Table 6.1 to describe what is observed when the named reagent is added to an aqueous solution of cobalt( II ) chloride.
Table 6.1
| reagent | colour of cobalt-containing product | state of cobalt-containing product |
| :--- | :---: | :---: |
| NaOH(aq) | | |
| an excess of conc. HCl | | |
(ii) Write an equation for the reaction between $[\text{Co}(\text{H}_{2}\text{O})_{6}]^{2+}$ ions and NaOH(aq).
[1]
(iii) Write an equation for the reaction between $[$ Co($\text{H}_{2}\text{O}$)$_{6}]$^{2+}$ ions and an excess of conc. HCl.
[1]
(b) (i) Define stability constant.
[1]
(ii) Write an expression for the stability constant, $K_{\7 (a) The structural and displayed formulae of three aromatic compounds, A, B and C, are shown in Fig. 7.1.
$$\text{C}_6\text{H}_5\text{CH}_2\text{CH}_2\text{COOH}$$
$$\text{CH}_3\text{C}_6\text{H}_4\text{OH}$$
$$\text{C}_6\text{h}_5\text{CH}_2\text{Cl}\text{CO}_2\text{H}$$
Fig. 7.1
Compare the relative acidities of A, B and C.
most acidic > least acidic
Explain your answer.
[3]
(b) Methylbenzene, $C_6\text{H}_5\text{CH}_{3}$, can be made from benzene by an electrophilic substitution reaction.
(i) Identify a compound that reacts with benzene to form methylbenzene.
Identify the catalyst used.
compound ..... catalyst ..... [1]
(ii) The first step in the reaction is the generation of the $\text{CH}_3^+$ electrophile.
Write an equation for the reaction that generates this electroph(iii) Describe the mechanism for the reaction between benzene and the $CH_3^+$ electrophile. Include all relevant curly arrows and charges.
$$\text{CH}_3^+ \rightarrow \text{CH}_3^+$$
[3]
(iv) Identify a suitable reagent to oxidise methylbenzene to benzoic acid, $C_6H_5COOH$. Write an equation for this reaction using [O] to represent one atom of oxygen from the oxidising agent.
reagent .....
equation ..... [2]
(v) Methylbenzene and benzoic acid are both nitrated with a mixture of concentrated nitric acid and sulfuric acid to give mononitrated products. The structural formulae of these products are $CH_3C_6H_4NO_2$ and $HOOCC_6H_4NO_2$ respectively.
Draw the structures of these two products.(c) A reaction scheme is shown in Fig. 7.2.
Fig. 7.2
(i) Describe the reagents and conditions to produce CH$_3$C$_6$H$_4$N$_2^+$Cl$^{-}$ from CH$_3$C$_6$H $_4$NH$_2$ in reaction 2.
reagents ..... [1]
(ii) Describe how CH$_3$C$_6$H}_4\text{OH} can be produced from CH$_3$C$_6$Hz$_4$N$_2^+$ Cl$^{-}$ in reaction 3.
[1]
(iii) Draw the structure of the dye molecule Y formed when CH$_3$C$_6$Hz}_4\text{N}_2^+$ Cl$^{-}$ and CH$_3$C$_6$Hz $_4$OH react together in reaction 4. Describe the conditions for this reaction.
structure
conditions ..... [2]
[Total: 15]8 When answering this question it should be assumed that together all the hydrogen atoms in a benzene ring result in a single unsplit peak at $\delta = 7.2$ in a proton ($^1\text{H}$) NMR spectrum. The structures of five isomeric ketones, P, Q, R, S and T are given.
P $C_6H_5COCH(CH_3)_2$
S $C_6H_5CH_2CH_2COCH_3$
Q $C_6H_5COCH_2CH_2CH_3$
T $C_6H_5CH(CH_3)COCH_3$
R $C_6H_5CH_�COCH_2CH_3$
(a) Identify all the chiral carbon atoms on the structures above. Label each chiral carbon atom with an asterisk (*).
(b) The proton ($^1\text{H}$）NMR spectrum of one of the five isomers, P, Q, R, S or T, is shown in Fig. 8.1.
(i) Identify which of the compounds P, Q, R, S or T gives this spectrum.
Draw the displayed formula of the compound you have identified. Identify the protons r(c) Choose from the letters P, Q, R, S and T to identify: (i) the two compounds that each have a doublet peak in the proton (¹H) NMR spectrum (ii) the compound with only three peaks in its proton (¹H) NMR spectrom. (d) Suggest a suitable solvent that should be used for obtaining the spectrum shown in Fig. 8.1. (e) The proton (¹H) NMRpectrum of compound T is compared in the presence of D₂O and in the absence of D₂O. Describe any difference between the two spectra. Explain your answer. (f) Complete Table 8.1 below to give the number of peaks in the carbon-13 NMR spectrum of each compound. Table 8.1 | compound | number of peaks | compound | number of peaks | | :---: | :---: | :---: | :--- | Compound 1 | | Compound 2 | | | Compound 3 | | Compound 4 | | [Total: 10]
9 Tyrosine and lysine, shown in Fig. 9.1, are naturally occurring amino acids found in proteins. Fig. 9.1 (a) The isoelectric point of lysine is 9.47. Draw the structure of lysine at the stated pH in the boxes below. lysine at pH 7.00 lysine at pH 9.47 lysine at pH 12.00 (b) When ethanoic acid is treated with PC$l_5$ product D is formed. When D is added to tyrosine two different isomeric products, E and F, are formed. E has an ester linkage, F does not. Draw the structures of D, E and F in the boxes below. D E F
(c) Complete Table 9.1 by drawing the structure of the organic product formed when tyrosine reacts with each named reagent.
Ignore the directing effect of the $-\text{CH}_2\text{CHNH}_2\text{COOH}$ substituent.
Table 9.1
| reagent | structure |
| :--- | :--- |
| an excess of $\text{Br}_2(\text{aq})$ | |
| an excess of NaOH(aq) | |
| an excess of $\text{HNO}_3(\text{aq})$ | |
(d) A mixture of tyrosine and lysine can be separated by thin-layer chromatography. Under certain conditions the $R_f$ value of lysine is 0.14 and the $R_f$ value of tyrosine is 0.45.
(i) Explain what is meant by $R_f$ value.
[1]
(ii) Suggest an explanation for the difference in $R_f$ values.
[1]
Total: 10