科目：化学 Chemistry (9701)
年份：2025 春季
试卷：Paper 42
总页数：24
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, 29 Organic synthesis, 30 Analytical chemistry
1 Silver, Ag, is a metal in the d-block of the Periodic Table.
(a) Silver can form compounds containing either $Ag^+$ or $Ag^{2+}$ ions.
Explain why silver is a transition element.
[1]
(b) Table 1.1 gives data relevant to the Born–Haber cycle for silver(I) fluoride, AgF.
Table 1.1
| standard energy change | value/kJ mol$^{-1}$ |
| :--- | :--- |
| first ionisation energy of silver | +732 |
| enthalpy change of atomisation of silver | +289 |
| enthalpy change of atomisationof fluorine | +79 |
| enthalpy change of formation of silver(I) fluoride | –203 |
| lattice energy of silver(I) fluoride | –955 |
(i) Write equations for the standard enthalpy changes described.
Include state symbols.
• standard enthalpy change of atomisation of silver
• standard enthalpy change of formation of sil(iii) Calculate the first electron affinity, $EA_1$, of fluorine, using data from Table 1.1.
It may be helpful to draw a labelled energy cycle as part of the working for your answer.
$$EA_1 = \text{kJ mol}^{-1}$$
(c)(i) Use the data in Table 1.2 to calculate the enthalpy change of solution, $\Delta H_{\text{sol}}$, of AgF(s).
Table 1.2
| energy change at 298 K | value / kJ mol$^{-1}$ |
| :--- | :--- |
| lattice energy of AgF(s) | –955 |
| enthalpy change of hydration of Ag$^+$(g) | –464 |
| enthalpy change of hydrationof F$^-$(g) | –506 |
$\Delta H_{\text{sol}}$ of AgF(s) = ……………………… kJ mol$^{-1}$
(ii) Use your answer to (c)(i) to suggest whether AgF is soluble in water at 298 K. Explain your answer.
...(d) Table 1.3 shows some data relevant to the silver(I) halides, AgCl to AgI.
Table 1.3
| silver(I) halide | first electron affinity of halogen/kJ mol$^{-1}$ | lattice energy /kJ mol$^{-1}$ |
| :--- | :---: | :---: |
| AgCl | –349 | –905 |
| AgBr | –325 | –890 |
| AgI | –295 | –876 |
(i) Explain the trend in the first electron affinities of the halogens, Cl to I.
[2]
(ii) Explain the trend in the lattice energies of the silver(I) halides, AgClto AgI.
[1](e) An electrochemical cell is constructed using the electrodes shown in Table 1.4.
Table 1.4
| electrode | half-equation | $E^\ominus$/V |
| :--- | :---: | ---: |
| 1 | $\text{AgCl}(s) + e^- \rightleftharpoons \text{Ag}(s) + \text{Cl}^-(aq)$ | +0.222 |
| 2 | $\text{Cu}^{2+}(\text{aq}) + 2\text{e}^- \rightleftharpoons \mathrm{Cu}(s)$ | +0.342 |
(i) Calculate the standard cell potential, $E^\ominus_{\text{cell}}$.
Construct an equation for the overall cell reaction.
$$E^\ominus_{\text{cell}} = \dots\dots\dots\dots\mathrm{V}$$
equation ... [2]
(ii) In a different experiment, electrode 1 is set up using a saturated solution of KCl.
Saturated KCl(aq) contains 36.0 g of KCl per 100 cm³ of solution at 298 K.
The Nernst equation for electrode 1 is:
$$E = E^\ominus + \frac{0.059}{z} \log \f2 Propanone, CH$_3$COCH$_3$, is a common organic solvent and reagent.
(a) Propanone reacts with methanol, CH$_3$OH, under acidic conditions to form compound A, as shown by reaction 1.
$$\text{CH}_3\text{COCH}_3 + 2\text{CH}_3\text{OH} \rightarrow \text{A}$$
Fig. 2.1
The overall order of reaction 1 can be found by studying experimental data.
Table 2.1 shows how the initial rate of reaction changes as [CH$_3$OH] and [H$^+$] are varied. In each experiment, a large excess of CH$_3$COCH$_3$ is used.
| experiment | $[\text{CH}_3\text{OH}] / \text{mol dm}^{-3}$ | $[\text{H}^+] / \text{mol dm}^{-2}$ | relative initial rate of reaction |
| :--- | :---: | :---: | :---: |
| 1 | 0.010 | 0.010 | 1.00 |
| 2 | 0.015 | 0.015 | 2.25 |
| 3 | 0.015 | 0.020 | 3.00 |
(i) Explain why a large excess of C(iii) In a separate experiment, a large excess of CH$_3$OH and H$^+$ ions are added to a solution containing a known concentration of CH$_3$COCH$_3$. Fig. 2.2 shows how [CH$_3$COCH$_3$] varies over time. % of the original [CH$_3$COCH$_3]$ remaining Fig. 2.2 Use Fig. 2.2 to show how, under these conditions, reaction 1 is first order with respect to CH$_3$COCH$_3$.
(b) Propanone also reacts with acidified cyanide ions to form the hydroxynitrile compound B, as shown by reaction 2.
$$\text{CH}_3\text{COCH}_3 + \text{H}^+ + \text{CN}^- \rightarrow \text{B}$$
Fig. 2.3
The following rate equation is determined for reaction 2.
$$\text{rate} = k [\text{CH}_3\text{COCh}_3] [\text{H}^+]$$
Four possible mechanisms for reaction 2 are shown in Table 2.2.
Table 2.2
| proposed reaction mechanism | steps |
| :--- | :--- |
| 1 | fast $\text{CH}_3\text{COCH}_{3} + \text{H}^{+} \rightarrow [\text{CH}_3\text{C(OH)CH}_3]^{+}$ slow $[\text{CH}_3\text{C( OH ) CH}_3]^{+} + \text{CN}^{-} \rightarrow \text{CH}_3\text{C( O H ) ( C N ) CH}_3$ |
| 2 | fast $\text{H}^{+} + \text{CN}^{-}\rightarrow \text{HCN}$ slow $\text{CH}_3\text{COCh}_{3} + \text{HCN} \rightarrow \text(c) Carboxylic acid C, $C_4H_8O_3$, forms when B is hydrolysed under hot acidic conditions.
(i) Draw the structure of C.
[1]
(ii) The p$K_a$ of C is 3.95. Calculate the pH of a 0.500 mol dm$^{-3}$ solution of C.
Show your working.
$$\text{pH} = \dots$$
(d) C can be used to form buffer solution D.
(i) Define a buffer solution.
....
....
....
[2]
(ii) Buffer solution D is made when 20.0 cm$^3$ of 1.00 mol dm$^{-3}$ NaOH(aq) is added to 100 cm$^3$
of a 0.500 mol dn$^{-3}$ solution of C.
The p$K_a$ of C is 1.95.
Calculate the pH of buffer solution D.
Show your working.
$$\text{P H} = \dots$$
[Total: 15]3 Fe$^{2+}$ and Fe$^{3+}$ ions are able to form a variety of complexes with different species.
(a) (i) Define complex.
[1]
(ii) Table 3.1 gives some details of different complexes of Fe$^{2+}$ and of Fe$^{3+}$.
Complete Table 3.1.
Table 3.1
| complex | ion | ligand | coordination number | formula and charge of complex |
| :---: | :---: | :---: | : ---: | :---: |
| E | Fe$^{2+}$ | NH$_3$ | 6 | |
| F | | | | [FeCl$_4$]$^2-$ |
| G | | en | | [Fe(en)$_3$]$^3+$ |
(iii) Complete Fig. 3.1 to show the splitting of the d-orbitals in a tetrahedral complex.
Fig. 3.1
[1](b) Table 3.2 gives details of some complexes of Fe$^{3+}$.
Table 3.2
| complex | colour | value of $K_{\text{stab}}$ |
| :--- | :---: | :---: |
| $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$ | violet | 1 |
| $[\text{Fe}(\text(H}_2\text{O})_5\text{SCN}]^{2+}$ | red | $1.40 \times 10^2$ |
| $[\text{Fe}(\text,H}_2\text{O})_5\text F]^{2+}$ | colourless | $2.40 \times 10^5$ |
(i) Explain the reason for the difference in colour of the two complexes $[\text{Fe}(\text{H}_{2}\text{O})_{6}]^{3+}$ and $[\text{Fe}(\text{H_{2}O})_{5}\text{SCN}]^{2+}$.
[2]
(ii) Write an expression for $K_{\text{stab}}$ of $[\text{Fe}(\text{H} _2\mathrm{O})_5\text{SCN}]$$^{2+}$.
$$K_{\text{stab}} =$$
[1]
(iii) Use information in Table 3.2 to calculate the value of the equilibrium constant, $K_c$, for the following r(c) Hydrated compound J, $K_3Fe(C_2O_4)_3 \cdot xH_2O$, contains the green complex ion $[Fe(C_2O_4)_3]^{3-}$.
The value of $x$ can be determined by titration of a sample of J with acidified MnO$_4^-$ ions. MnO$_4^-$ ions oxidise $C_2O_4^{2-}$ ions in acidic conditions.
$$2MnO_4^{-} + 5C_2O_4^{2-} + 16H^+ \rightarrow 2Mn^{2+} + 10CO_2 + 8H_2O$$
(i) Write half equations for the oxidation of $C_2O_4^{2-$ ions and for the reduction of MnO$_4^-$ ions.
• oxidation of $C_2O__{4}^{2-}$
....
• reduction of $MnO_4^{-}$
....
(ii) A student prepares a solution containing 0.100 g of J.
The student titrates this solution with 0.0200 mol dm$^{-3}$ acidified KMnO$_4$(aq). The titre obtained is 12.20 cm$^3$.
Assume all of the $C_2O_4^{2$- ions are oxidised.
Calculate the value of $x$ in $K_3Fe(C_24 (a) State the difference in the basicities of ammonia, NH$_3$, propanamide, CH$_3$CH$_2$CONH$_2$, and propylamine, CH$_3$CH$_2$CH$_2$NH$_2$.
Explain your answer.
[4]
(b) Fig. 4.1 shows two different ways to synthesise propylamine.
$$\text{K} \rightarrow \text{NH}_3 \rightarrow \text{CH}_3\text{CH}_2\text{CONH}_2 \quad M \rightarrow \text{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{NH}_2$$
$$\text{CH}_3\text{CH}_�\text{Br} \xrightarrow{\text{KCN in ethanol}} L \quad M$$
Fig. 4.1
Identify compounds K and L and reagent M from Fig. 4.1.
K ....
L ....
M ....[3]Compound N is treated with an excess of concentrated HCl(aq). N undergoes complete hydrolysis to form three organic products. The products are isolated from the reaction mixture at pH4. Draw the structures of the three organic products at pH4. Assume that the CH$_3$O— group does not react.
(d) Compound P can be synthesised from 1-methyl-4-nitrobenzene by the route shown in Fig. 4.3.
1-methyl-4-nitrobenzene
Fig. 4.3
(i) Step 1 is a reduction reaction.
Complete the equation for this reaction. Use [H] to represent an atom of hydrogen from the reducing agent.
$$\text{C}_7\text{H}_7\text{NO}_2 + \dots$$ [1]
(ii) Complete Table 4.1 to give details of each step of the synthesis shown in Fig. 4.3.
Table 4.1
| step | reagents and conditions | type of reaction |
| :--- | :---: | :---: |
| 1 | | reduction |
| 2 | | |
| 3 | | |
| 4 | | condensation |
[Total: 18]5 Cumene is an aromatic hydrocarbon used in the synthesis of other useful chemicals.
Fig. 5.1
(a) Complete Table 5.1 to show the number of sp² and sp³ hybridised carbon atoms that are present in a molecule of cumene.
Table 5.1
| type of hybridisation | sp² | sp³ |
| :--- | :--- | :--- |
| number of carbon atoms | | |
(b) Cumene can be synthesised via a Friedel–Crafts alkylation reaction, as shown in Fig. 5.2.
Fig. 5.2
(i) Name the mechanism involved in the Friedel–Crafts alkylation shown in Fig. 5.2.
[1]
(ii) The first step of the reaction forms the $(\text{CH}_3)_2\text{CH}^+$ cation.
Identify a suitable reagent for the formation of this cation from 2-bromopropane, $(\text{CH}_3)_2\text{CHBr}$.
[1](iii) Complete Fig. 5.3 to show the mechanism for the reaction of benzene with the $(\text{CH}_3)_2\text{CH}^+$ cation.
Include all relevant curly arrows and charges.
(iv) The Friedel–Crafts alkylation of benzene by 1-bromopropane, $\text{CH}_3\text{CH}_2\text{CH}_2\text{Br}$, also produces cumene as the major product.
The $\text{CH}_3\text{CH}_{2}\text{CH}_{2}^{+}$ cation formed in the first step quickly rearranges to form the $(\text{CH}_3)__{2}\text{CH}^{+}$ cation.
Suggest why this is the case. Explain your answer.
[1](c) Cumene oxidises in air to form phenol, $C_6H_5OH$, and propanone, $\text{CH}_3\text{COCH}_3$.
reaction 1: $C_6H_5\text{CH}(\text{CH}_3)_2 + \text{O}_2 \rightarrow C_6H_5\text{OH} + \text{CH}_3\text{COCH}_{3}$ $\Delta H^\circ = -371 \text{ kJ mol}^{-1}$
Table 5.2 gives some relevant standard entropies for reaction 1.
| compound | $C_6H_5\text{ CH}(\text{CH}_3)_2$ | O$_2$ | $C_6H_5\text OH$ | $\text{CH}_3\text{ COCH}_3$ |
| :--- | :--- | :--- | :--- | ---: |
| standard entropy, $S^\circ / JK^{-1}\text{mol}^{-1}$ | 278 | 205 | 146 | 200 |
(i) Calculate the standard entropy change, $\Delta S^\circ$, of reaction 1.
$$\Delta S^\circ = ... \text{ JK}^{-1}\text{mol}^{-1}$$ [1]
(ii) Show that reaction 1 is feasible at $25^{\circ}\text{C}$.(d) Fig. 5.4 shows two reactions of phenol. (i) State the conditions for the bromination of phenol in reaction 2. Explain why these conditions are different from those for the bromination of benzene. conditions ... explanation ... [4] (ii) Draw the structure of organic compound Q in Fig. 5.4. [1] (iii) Identify organic reagent R. [1] (iv) Name the functional group that is formed in reaction 3. ... [1]
(v) The reaction of phenol with HNO$_3$ produces a mixture of isomers with molecular formula C$_6$H$_5$NO$_3$. Identify the two isomers that are produced in the largest quantities. Explain your answer. explanation ..... [2] [Total: 19]
Question 6 starts on the next page.
6 (a) Maleic anhydride is an unsaturated cyclic compound used in the formation of several polymers.
Maleic anhydride can be used to form maleic acid and tartaric acid.
$$\text{maleic anhydride} \xrightarrow{\text{reaction 1}} \text{maleic acid} \xrightarrow{\text{re reaction 2}} \text{Tartaric acid}$$
Fig. 6.1
(i) Maleic acid reacts with ethane-1,2-diol to form a condensation polymer.
Draw a section of this polymer, showing only one repeat unit.
The new functional group formed should be shown fully displayed.
[2]
(ii) Identify a suitable reagent and the conditions for reaction 2.
... [1](b) Compound U can be formed from tartaric acid in two steps, as shown in Fig. 6.2.
tartaric acid
$$\text{CH}_3\text{COCH}_3 \quad \text{and} \quad H^+$$
step 1
step 2
Fig. 6.2
(i) Suggest the type of reaction that occurs in step 1.
[1]
(ii) U can act as a bidentate ligand.
Explain what is meant by a bidentate ligand.
[2]
(iii) Complete the three-dimensional diagrams in Fig. 6.3 to show both stereoisomers of $[\text{Cu(U)}_3]^{4-}$.
Use O to represent ligand U.
Fig. 6.3
[2](c) A student analyses an aromatic compound, X, C₈H₈O₃, using NMR spectroscopy. Fig. 6.4 shows the carbon-13 NMR spectrum of a sample of X dissolved in D₂O. Fig. 6.4 Separate samples of X were analysed using proton (¹H) NMR spectroscopy. Table 6.1 gives information obtained from this analysis. <table><thead><tr><th>solvent</th><th>number of signals in proton (¹H) NMR spectrum</th></tr></thead><tbody><tr><td>CDCl₃</td><td>6</td></tr><tr><td>D₂O</td><td>4</td></tr></tbody> (i) Identify the number of different carbon environments present in X. [1] (ii) Explain why X is dissolved in D₂O before obtaining its proton (¹H) NMRpectrum. [1]
(iii) Aromatic compound X gives a yellow precipitate when it reacts with alkaline I$_2$(aq).
Use the information in (c) to suggest a structure for X.
Explain your reasoning.
$$\text{X}, \text{C}_8\text{H}_8\text{O}_3$$
[4]
Table 6.2
| environment of carbon atom | example | carbon-13 NMR chemical shift range $\delta$/ppm |
| :--- | :--- | :--- |
| alkyl | CH$_3$-, CH$_2$-, -CH<, >C< | 0–50 |
| next to alkene/arene | -C-C=C, -C-Ar | 25–50 |
| next to carbonyl/carboxyl | C-COR, C-O$_2$R | 30–65 |
| next to halogen | C-X | 30–60 |
| next to oxygen | C-O | 50–70 |
| alkene or arene | >C=C<, C-C-C | 110–160 |
| carboxyl | R-COOH, R-COOR | 160–185 |
| carbonyl | R-CHO, R-CO-R | 190–220 |
| nitrile | R-C≡N | 100–125 |
[Total: 14]