科目：化学 Chemistry (9701)
年份：2024 夏季
试卷：Paper 42
总页数：20
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, 28 Polymerisation, 30 Analytical chemistry
1. (a) Describe the trend in the solubility of the sulfates of magnesium, calcium and strontium.
Explain your answer.
most soluble > least soluble
[4]
(b) Define lattice energy, $\Delta H_{\text{latt}}$.
[2]
(c) State and explain the main factors that affect the magnitude of lattice energies.
[2]
(d) Table 1.1 shows some energy changes.
Table 1.1
| energy change | value / kJ mol⁻¹ |
| :--- | :---: |
| standard enthalpy change of atomisation of potassium | +89 |
| first ionisation energy of potassium | +419 |
| second ionisation energy of potassium | +3070 |
| standard enthalpy change of atomisations of sulfur | +279 |
| S–S bond energy | +265 |
| first ionisation energy of sulfur | +1000 |
| second ionisation energy of sulfur | +2260 |
| first electron affinity of sulfur | −200 |(i) Born–Haber cycles can be used to determine the lattice energies of ionic compounds. Complete the Born–Haber cycle in Fig. 1.1 for potassium sulfide, K$_2$S(s). Include state symbols for all of the species.
(ii) Calculate the lattice energy, $\Delta H_{\text{latt}}^\ominus$, of K$_2$S(s) using relevant data from Table 1.1. Show your working.
$$\Delta H_{\text{latt}}^\circ \text{ of } K_2\text{S}(s) = \dots\dots\dots\dots\kappa J \text{ mol}^{-1}$$
[Total: 13]2 (a) (i) Lithium nitrate, LiNO$_3$, decomposes on heating in a similar way to Group 2 nitrates to give the metal oxide, a brown gas and oxygen.
Write an equation for the decomposition of LiNO$_3$.
[1]
(ii) The other Group 1 nitrates, MNO$_3$, decompose on heating to form the metal nitrite, MNO$_2$, and oxygen.
The thermal stability of these nitrates increases down the group.
Suggest why the thermal stability of MNO$_3$ increases down the group.
[2]
(b) Acidified manganate(VII) ions, MnO$_4^-$, can be used to analyse solutions containing nitrite ions, NO$_2^-$, by titration.
X is a solution of NaNO$_2$.
250.0 cm$^3$ of X is added to 50.0 cm$^3$of 0.125 mol dm$^{-3}$ acidified MnO$_4^$- (aq). The MnO$_4^$- (aq) ions are in excess; all the NO$_2^-$ ions are oxidised in the reaction.(c) Table 2.1 shows electrode potentials for some electrode reactions involving manganese compounds.
Table 2.1
| electrode reaction | $E^\ominus$/V |
| :--- | :--- |
| $\text{Mn}^{2+} + 2\text{e}^- \rightleftharpoons \text{Mn}$ | $-1.18$ |
| $\text{MnO}_2 + 4\text{H}^+ + 2\text{e}^- \Rightarrow \text{Mn}^{2+} + \text{2H}_2\text{O}$ | $+1.23$ |
| $\text{MnO}_{4}^- + \text{e}^- \Rightarrow \text{\text{MnO}}_{4}^{2-}$ | $+0.56$ |
| $\text{MnO}_{\text{4}}^{-} + 4\text{H}^+ + \text{3e}^- \Rightarrow \text{\mathrm{MnO}}_2 + \text{2H}_2\text{\text{O}}$ | $+1.67$ |
| $\text{MnO}{\text{4}}^{-} + 8\text{H}^+ + \text{5e}^- \Rightarrow \text{\mathbf{Mn}}^{2+} + \text{4H}_2\text{\text{O}} $ | $+1.52$ |
| $\text{MnO}{4}^{-} + 2\text{H}_2\text{\text{O}} + \text{3e}^- \rightleftharpoonup \text{\mathrm{M3 (a) Carbon disulfide, CS$_2$, is flammable and reacts readily with oxygen, as shown in reaction 1.
reaction 1 $\text{CS}_2(\text{g}) + 3\text{O}_2(\text{g}) \rightarrow \text{CO}_2(\text{g}) + 2\text{SO}_2(\text{g})$
Table 3.1 shows the standard enthalpy of formation, $\Delta H_f^\ominus$, and the standard entropy, $S^\ominus$, for some substances.
| | $\text{CS}_2(\text{(g))}$ | $\text{O}_2(\text{(g))}$ | $\text{CO}_2(\text{(g))}$ |
| :--- | :---: | :---: | :---: |
| $\Delta H_f^\ominus / \text{kJ mol}^{-1}$ | 116.7 | 0.0 | -393.5 |
| $S^\ominus / \text{J K}^{-1} \text{mol}^{-1}$ | 237.8 | 205.2 | 213.8 |
Calculate the standard Gibbs free energy change, $\Delta G^\ominus$, in kJ mol$^{-1}$, for reaction 1 at 25°C.
$$\Delta G^\ominus = \dots\dots\dots\dots\mathrm{kJ mol}^{-1}$$
(b)4 (a) (i) Explain why transition elements have variable oxidation states.
(ii) Sketch the shape of a 3d$_{2^2}$ orbital in Fig. 4.1.
Fig. 4.1
(b) Samples of $[\text{Cu(H}_2\text{O})_6]^{2+}(\text{aq})$ are reacted separately with an excess of solution A and with an excess of solution B.
The reaction of $[\text{Cu(H}_2\text{O})_6]^{2+}$(aq) with solution A is a precipitation reaction.
The reaction of $[\text{Cu}(H_2\text{O})_6]^{3+}$(aq) with solution B is a ligand substitution reaction.
Suggest a possible identity for solution A and for solution B. Give relevant observations and the formula of the copper-containing product for each reaction.
solution A ..... observations ..... formula of the copper-containing product ..... solution B ..... observations ..... formula of the copper-co(c) Solutions containing the $[\text{Ag(NH}_3)_2]^+$ complex are colourless.
Explain why this complex is colourless.
[2]
(d) Two bidentate ligands are shown in Fig. 4.2.
Fig. 4.2
Explain what is meant by a bidentate ligand.
[2](e) Ruthenium(III) ions, Ru$^{3+}$, form an octahedral complex, $[\text{Ru}(dpys)_2\text{Cl}_2]^+$, with the ligands dpys and chloride ions.
This complex shows the same kind of stereoisomerism as $[\text{Ru}(\text{NH}_3)_4\text{Cl}_2]^+$ but also shows a different type of stereoisomerism.
(i) Complete the three-dimensional diagrams in Fig. 4.3 to show the three different stereoisomers of $[\text{Ru}(dpys)__2\text{Cl}_2]^+$.
The dpys ligand can be represented using N N.
(ii) State the different types of stereoisomerism shown by $[\text{Ru}(dpys)_ _2\text{Cl}_2]^+$. [1]
(iii) Deduce which stereoisomers in (e)(i) are non-polar. Explain your answer. [1]
[Total: 14]5 (a) Nitrosyl chloride, $NOCl$, can be formed by the reaction between nitrogen monoxide and chlorine, as shown.
$$2NO + Cl_2 \rightarrow 2NOCl$$
The initial rate of this reaction is investigated, starting with different concentrations of NO and $Cl_2$. The results obtained are shown in Table 5.1.
| experiment | [NO]/mol dm$^{-3}$ | [$Cl_2$/mol dm$^{-3}$] | initial rate/mol dm$^{-3}$ min$^{-1}$ |
| :--- | :---: | :---: | :---: |
| 1 | 0.0250 | 0.0150 | $3.68 \times 10^{-2}$ |
| 2 | 0.0750 | 0.015O | $3.32 \times 10^{-1}$ |
| 3 | 0.0500 | 0.0600 | $5.89 \times 10^{-1}$ |
(i) Use the data in Table 5.1 to deduce the rate equation for this reaction.
Explain your reasoning.
[3]
(ii) Use your rate equation from (a)(i) and the data from experiment 1 to calculate the rate constant, $k$, for(b) NO$_2$Cl is another compound containing nitrogen, oxygen and chlorine.
In sunlight, NO$_2$Cl can undergo homolytic fission to release chlorine radicals which can catalyse the conversion of ozone, O$_3$, into oxygen.
Complete the mechanism for this process.
initiation (homolytic fission) $\text{NO}_2\text{Cl} \rightarrow$ ..... + .....
propagation step 1 ...+ $O_3 \rightarrow$ ..... +
propagation step 2 ...+ ..... → ..... + .....
(c) Ozone reacts with nitrogen dioxide, as shown.
$$\text{O}_3 + 2\text{NO}_2 \rightarrow \text{N}_2\text{O}_5 + \text{O}_2$$
The rate of reaction is first order with respect to O$_3$ and first order with respect to NO$_2$.
Suggest equations for a two-step mechanism for this reaction.
step 1 ......
step 2 ..... [Total: 9]6 (a) Aqueous solutions of methanoic acid, HCOOH, and propanoic acid, CH$_3$CH$_2$COOH, are mixed together.
An equilibrium is set up between two conjugate acid–base pairs.
(i) Define conjugate acid–base pair.
[1]
(ii) The $pK_a$ of HCOOH is 3.75 and of CH$_3$CH$_2$COOH is 4.87.
Complete the equation for the Brønsted–Lowry equilibrium between the stronger of these two acids and water.
$$+ \text{H}_2\text{O} \rightleftharpoons +$$
[1]
(b) (i) Write an expression for the acid dissociation constant, $K_a$, for butanoic acid, CH$_3$CH $_2$CH$_2$COOH.
$$K_a =$$
[1]
(ii) The $p K_a$ of CH$_3$CH$_2$CH$_2$COOH is 4.82.
A solution of CH$_3$CH$_2$Ch$_2$COOH(aq) has a pH of 3.25.
Calculate the concentration, in mol dm$^{-3}$, of CH$_3$CH$_2$ch$_2$COOH in this solution.
concentration of C(ii) A buffer solution containing a mixture of CH$_3$COOH and CH$_3$COONa is prepared as follows.
A solution of 600 cm$^3$ of CH$_3$COOH is mixed with 400 cm$^3$ of 0.125 mol dm$^{-3}$ CH$_3$COONa.
The buffer solution has pH 5.70. The $K_a$ of CH$_3$COOH is $1.78 \times 10^{-5}$ mol dm$^{-3}$.
Calculate the initial concentration, in mol dm$^{-3}$, of CH$_3$COOH used.
concentration of CH$_3$COOH = ..... mol dm$^{-3}$ [3]
(d) A fuel cell is an electrochemical cell that can be used to generate electrical energy by using oxygen to oxidise a fuel.
Methanoic acid, HCOOH, is being investigated as a fuel in fuel cells.
When the cell operates, HCOOH is oxidised to carbon dioxide.
The half-equation for the reaction at the cathode is: O$_2$ + 4H$^{+}$ + 4e$^{-}$ $\rightarrow$ 2H$_2$O.
In thi7 Methyl red can be synthesised as shown in Fig. 7.1. Fig. 7.1
(a) (i) Give the systematic name of P. (ii) P can be synthesised as shown in Fig. 7.2.  Suggest reagents and conditions for this reaction. (iii) A student attempts to synthesise P by an alternative route, as shown in Fig. 7.3. Compound T is the major product in this reaction rather than P.  Explain why T is the major product in this reaction. (b) S reacts in a similar way to phenol in step 3. (i) Draw the structures of Q, R and S in the boxes in Fig. 7.1. (ii) Suggest reagents and conditions for steps 1 and 2 in Fig. 7.1. step 1 ..... step 2 [Total: 9]
8 (a) State the relative basicities of phenylamine, $C_6H_5NH_2$, benzylamine, $C_6H_5CH_2NH_2$, and ammonia, NH$_3$, in aqueous solution. Explain your answer. most basic > least basic [3] (b) An excess of Br$_2$(aq) is added to separate samples of $C_6H_5NH_Z$ and benzene, $C_6H_6$. (i) $C_6H_5NH_ Z$ reacts readily with Br$_2$(aq) to form organic product M. State the expected observations for this reaction. Draw the structure of M. observations ... structure of M [2] (ii) $C_6H_6$ does not react with Br$_2$(aq). Suggest why Br$_2$(aq) reacts with $C_6H_5NH_ 2$ but not with $C_6H_6$. [2] (c) Explain why benzamide, $C_6H_5CONH_2$, is a much weaker base than ammonia, NH$_3$.
(d) $C_6H_5CONH_2$ is formed by reacting benzoyl chloride, $C_6H_5COCl$, with $\text{NH}_3$.
Complete the mechanism in Fig. 8.1 for the reaction of $C_6H_5COCl$ with $\text{NH}_3$.
Include all relevant lone pairs of electrons, curly arrows, charges and dipoles. Draw the structure of the organic intermediate.
[4](e) Phenylalanine, $C_6H_5CH_2CH(NH_2)COOH$, is an amino acid with an isoelectric point of 5.5. (i) State what is meant by isoelectric point. [1] (ii) Draw the structure of $C_6H_5CH_�CH(NH_2)COOH$ at pH 10. [1] (f) $C_6H_5CH_₂CH(NH_₂)COOH$ and alanine, $CH_3CH(NH_₂)COOH$, react to form a dipeptide containing both amino acid residues. Draw the structure of this dipeptide. The peptide functional group formed should be displayed. [2] [Total: 16]
(a) Explain why trichloroethanoic acid, CC$l_3$COOH, is more acidic than ethanoic acid, CH$_3$COOH. (b) Acyl chlorides are formed by reacting carboxylic acids with thionyl chloride, SOC$l_2$. (i) Ethanedioyl chloride, (COC$l_2$), can be prepared by reacting ethanedioic acid, (COOH)$_2$, with an excess of SOC$l_2$. Write an equation for this reaction. (ii) Samples of (COC$l_2$) are reacted separately with an excess of warm acidified KMnO$_4$(aq) and with H$_2$NCH$_2$CH$_2$NH$_2$. The carbon-containing product from the reaction with H$_2$NCH$_2$$CH_2$$NH$_2$ has the molecular formula C$_4$H$_6$N$_2$O$_2$. Complete the boxes in Fig. 9.1 to suggest the structure of the carbon-containing product in each reaction. with warm acidified KMnO$_4$((aq)) with H$_2$NCH$_2$$Ch_2$$NH$_2$ Fig. 9.
(c) Compound H, C$_6$H$_{10}$O$_3$, reacts with alkaline I$_2$(aq) to form yellow precipitate J but does not react with Na$_2$CO$_3$(aq).
The proton (^1H) NMR spectrum of H in CDCl$_3$ is shown in Fig. 9.2.
Fig. 9.2
Table 9.1
| environment of proton | example | chemical shift range $\delta$/ppm |
| :--- | :--- | :--- |
| alkane | $-CH_3$, $-CH_2-$, >CH– | 0.9–1.7 |
| alkyl next to C=O | CH$_3$-C=O, $-CH_2$-C=O, >CH–C=O | 2.2–3.0 |
| alkyl next to aromatic ring | CH$_3$-Ar, $-CH_2$-Ar, >CH–Ar | 2.3–3.0 |
| alkyl next到 electronegative atom | CH$_3$-O, $-CH_2$-O, $-CH_2$-Cl | 3.2–4.0 |
| attached to alkene | =CHR | 4.5–6.0 |
| attached to aromatic ring | H–Ar | 6.0–9.0 |
| aldehyde | HCOR | 9.3–10.5 |
| alcohol | ROH | 0.5–6.0 |
| phenol | Ar–OH | 4.5–7.0 |
| carboxylic acid | RCOOH | 9.0(i) Identify yellow precipitate J.
(ii) Complete Table 9.2 for the proton ($^1\text{H}$) NMR spectrum of H, $C_6H_{10}O_3$.
Table 9.2
| chemical shift $\delta$/ppm | splitting pattern | number of $^1\text{H}$ atoms responsible for the peak | number of protons on adjacent carbon atoms |
| :--- | :--- | :--- | :--- |
| 1.15 | | | |
| 2.25 | | | |
| 3.60 | | | |
| 3.95 | | | |
(iii) Suggest a structure for H, $C_6H_{12}O_3$. [Total: 12]