科目：化学 Chemistry (9701)
年份：2025 冬季
试卷：Paper 44
总页数：21
章节：19 Lattice energy, 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
(a) Define a transition element.
(b) The 3d orbitals in an isolated gaseous Cu$^{2+}$ ion are degenerate.
(i) Define the term degenerate.
[1]
(ii) Complete the electronic configuration of Cu$^{2+}$.
1s$^2$ ..... [1]
(c) (i) State the colours of the aqueous solutions for the two copper(II) complex ions shown.
• $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}(\text{aq})$
• $[\text{CuCl}_4]^{2-}(\text{aq})$
[1]
(ii) Explain why aqueous complex ions of transition elements are usually coloured.
[3]
(d) (i) When an excess of NH$_3$(aq) is added to a solution of $[\text{CuCl}_4]_{2}^{2-}(\text{aq})$, $[\text{Cu(NH}_3)(\text{H}_2\text{O})]_{2}^{2+}(\text{aq})$ is formed.
State the type of reaction.
Complete the equation for this reaction. State symbols are not required.
type of reactio(ii) The $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$ complex ion shows stereoisomerism.
Complete the three-dimensional diagrams in Fig. 1.1 to show the two different stereoisomers of $[\text{Cu(NH}_3)(\text{H}_2\text{O})]^{2+}$.
(iii) Deduce which stereoisomer in (d)(ii) is polar.
Explain your answer.
polar isomer ..... explanation ..... [1]
(e) The dianion P can act as a tridentate ligand.
(i) Suggest how P can form three dative covalent bonds.
[1]
(ii) 2 moles of dianion P, $C_4H_5NO_4^{2-}$, react with 1 mole of aqueous cobalt(III) ions, $[\text{Co(H}_2\text{O)}_6]^{3+}$ to form 1 mole of complex ion Q.
Deduce the formula and charge of Q. [1](f) Table 1.1 shows values for the stability constants, $K_{\text{stab}}$, of some silver(I) complexes.
Table 1.1
| complex | value of $K_{\text{stab}}$ |
| :--- | :--- |
| $\text{[Ag(CN)}_2]^{-}(\text{aq})$ | $1.1 \times 10^{18}$ |
| $\text{[Ag(NH}_3)_2]^{+}(\text{aq})$ | $1.\!2 \times 10^7$ |
| $\text{[Ag(S}_2\text{O}_3)_2]^{3-}(\text{aq})$ | $2.9 \times 10^{13}$ |
(i) Define the stability constant of a complex.
[1]
(ii) Use the information in Table 1.1 to identify the most stable silver(I) complex.
Explain your answer.
most stable ...
explanation ..... [1](g) Sodium sulfite, Na$_2$SO$_3$, is used as a food preservative.
A 3.75 g sample of impure Na$_2$SO$_3$ is dissolved in distilled water and made up to 250 cm$^3$ in a volumetric flask.
10.0 cm$^3$ of this solution requires 18.70 cm$^3$ of acidified 0.0150 mol dm$^{-3}$ MnO$_4^{−}$ (aq) to reach the end-point.
The equation for the reaction is shown.
$$2\text{MnO}_4^{−} + 5\text{SO}_3^{2-} + 6\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 5\text{SO}_4^{2-} + 3\text{H}_2\text{O}$$
Calculate the percentage by mass of Na$_2$SO$_3$ in the sample.
percentage by mass of Na$_2$SO$__3$ = ..... [3]
[Total: 19]2 (a) The Group 2 sulfates and the Group 2 chromates show similar trends in solubility.
Suggest the trend in the solubility of the Group 2 chromates down the group.
Explain your answer.
[4]
(b) Silver(I) chromate, Ag$_2$CrO$_4$, is sparingly soluble in water.
(i) Write an ionic equation to show the equilibrium between solid Ag$_2$CrO$_4$ and its aqueous solution.
Include state symbols.
[1]
(ii) The value of the solubility product, $K_{\text{sp}}$, of Ag$_2$CrO$_4$ is $1.12 \times 10^{-12}$ at 298 K.
Calculate the equilibrium concentration of Ag$^+$, in mol dm$^{-3}$, in a saturated solution of Ag$_2$CrO$_4$-at 298 K.
equilibrium concentration of Ag$^+$ = ... mol dm$^{-3}$ [3](c) The hydrogenchromate ion, HCrO$_4^-$, is a weak acid. The $pK_a$ of HCrO$_4^-$ is 6.49.
(i) Calculate the pH of a 0.0250 mol dm$^{-3}$ HCrO$_4^-$ solution.
$$\text{pH} = \dots$$
(ii) HCrO$_4^-$ can show amphoteric behaviour.
State the formula of:
• the conjugate acid of HCrO$_4^-$ ...
• the conjugate base of HCrO$_4^-$. ... [1](d) Table 2.1 shows some energy changes.
Table 2.1
| energy change | value/kJmol$^{-1}$ |
| :--- | :--- |
| first ionisation energy of silver | +731 |
| second ionisation energy of silver | +2074 |
| first ionisation energy of sulfur | +1000 |
| second ionisation energy of sulfur | +2251 |
| first electron affinity of sulfur | –200 |
| second electron affinity of sulfur | +532 |
| enthalpy change of atomisation of sulfur | +279 |
| enthalpy change of formation of silver(I) sulfide, Ag$_2$S(s) | –33 |
| lattice energy of silver(I) sulfide, Ag$_�$S(s) | –2677 |
(i) Define the term first electron affinity.
[1]
(ii) Explain why the value for the second electron affinity of sulfur is positive.
[1]
(iii) Construct an equation for the lattice energy of Ag$_�$S.
Include state symbols.
[1](iv) Calculate the enthalpy change of atomisation, $\Delta H_{\text{at}}$, in kJ mol$^{-1}$, of silver using relevant data from Table 2.1.
It may be helpful to draw a labelled Born–Haber cycle.
Show your working.
$$\Delta H_{\text{at}} \text{ of silver} = \dots\dots\dots\dots\ldots\ldots\ldots\ldotting\ldots\ldots\ldotten\ldots\ldotten\ldotten\ldotten\dots\ldotten\ldotten \text{kJ mol}^{-1}$$
(e) Suggest how the magnitude for the lattice energy of Ag$_2$S(s) differs from the lattice energy of Cu$_2$S(s).
Explain your answer.
[Total: 18]3 (a) Define the term entropy.
(b) (i) Place one tick ($\checkmark$) in each row of Table 3.1 to show the sign of the entropy change, $\Delta S$, for each process.
Table 3.1
| process | $\Delta S$ is negative | $\Delta S$ is positive |
| :---: | :---: | :---: |
| steam condensing into water | | |
| solid KCl dissolving in water | | |
(ii) Chlorine trifluoride, $C l F_3$, decomposes on heating into its elements, as shown.
reaction 1 $$2 C l F_3(g) \rightarrow C l_2(g) + 3 F_2(g)$$
Standard entropies are shown in Table 3.2.
Table 3.2
| substance | $C l F_3(g)$ | $C l_2(g)$ | $F_2(g)$ |
| :---: | :---: :---: | :---: :--- | :---: |
| $S^\circ$/JK$^{-1}$mol$^{-1}$ | +281.6 | +223.1 | +203.0 |
Calculate the standard entropy change, $\Delta S^\circ$, in JK$^{-1}$mol$^{-1}$, for reaction (ii) The Gibbs equation is shown.
$$\Delta G^{\ominus} = \Delta H^{\ominus} - T \Delta S^{\ominus}$$
Fig. 3.1 shows values of the Gibbs free energy change, $\Delta G^{\ominus}$, in kJ mol$^{-1}$, at different temperatures, $T$, in K, for reaction 2.
Assume $\Delta H^{\ominus}$ and $\Delta S^{\ominus}$ values for this reaction remain constant over this temperature range.
**Fig. 3.1**
Use the gradient and intercept on the y-axis in Fig. 3.1 and the Gibbs equation to determine:
• $\Delta S^{\ominus}$, in J K$^{-1}$ mol$^{-1}$, for reaction 2
• the minimum temperature, $T$, in K, at which the reaction is feasible
• $\Delta H^{\ominus}$, in kJ mol$^{−1}$, for reaction 2.
$\Delta S^{\ominus}$ for reaction 2 = ..... J K$^{-1}$ m(a) Nitrogen monoxide, NO, reacts with hydrogen, as shown in reaction 3.
$$2\text{NO} + 2\text{H}_2 \rightarrow \text{N}_2 + 2\text{H}_2\text{O}$$
(i) The rate equation for reaction 3 is shown.
$$\text{rate} = k[\text{H}_2][\text{NO}]^2$$
Complete Table 4.1.
| the order of reaction with respect to $[H_2]$ | |
| :--- | :--- |
| the order of reaction with respect to [NO] | |
| the overall order of the reaction | |
(ii) Predict how the initial rate for reaction 3 changes when the concentration of NO is halved.
[1]
(iii) Predict how the initial rate for reaction 3 changes when the concentrations of NO and $H_2$ are both increased three times.
[1]
(iv) Suggest why reaction 3 is unlikely to proceed by a mechanism involving only a single step.
[1]
(v) Suggest equations for the three s(b) Iodine, $I_2$, reacts with thiosulfate ions, $S_2O_3^{2-}$, as shown in reaction 4.
$$2S_2O_3^{2-} + I_2 \rightarrow S_4O_6^{2-} + 2I^-$$
Reaction 4 is carried out in the presence of a large excess of $I_2$. Under these conditions, the reaction is first order with respect to $[S_2O_3^{2-}]$ and zero order with respect to $[I_2]$.
The half-life, $t_{\frac{1}{2}}$, for reaction 4 is 720 s under certain conditions.
Calculate the value of the rate constant, $k$, for reaction 4. Include the units of $k$.
$$k = \text{units}$$
(c) The reaction between iodide ions, $I^{-}(aq)$, and peroxydisulfate ions, $S_2 O_8^{2-}(aq)$, is catalysed by $Co^{3+}(aq)$. The mechanism is similar to the mechanism of this reaction when $Fe^{3+}(aq)$ is used as the catalyst.
(i) State the type of catalysis 5 (a) Describe and explain the shape of benzene. In your answer, include: • the shape and bond angle in the ring • the hybridisation of the carbon atoms • how orbital overlap forms $\sigma$ and $\pi$ bonds between the carbon atoms in the ring. [4] (b) Fig. 5.1 shows two reactions of benzoic acid.  (i) Suggest reagents and conditions for reaction 5 and for reaction 6 in Fig. 5.1. reaction 5 ... [2] reaction 6 ... [2] (ii) State the type of reaction for reaction 5 in Fig. 5.1. [1]
(c) In the electrophilic substitution of arenes, different substituents can direct to different ring positions.
(i) Describe the directing effect of the $-\text{CH}_2\text{CH}_3$ group.
Explain your answer.
[1]
(ii) The alkylation of arenes uses a mixture of $\text{CH}_3\text{CH}_2\text{Br}$ and $\text{FeBr}_3$ to generate the $\text{CH}_3\text{CH}^+$ electrophile.
Write an equation for the formation of the $\text{CH}_3\text{Ch}^+$ electrophile.
[1]
(iii) Complete the mechanism in Fig. 5.2.
Include all relevant curly arrows and charges. Draw the structure of the organic intermediate.
[3]
(iv) Write an equation to show how $\text{FeBr}_3$ is regenerated after the reaction in Fig. 5.2.
[1]
[Total: 13]6 (a) Compound Z is used in organic synthesis. Complete Table 6.1 to show the number of sp, sp² and sp³ hybridised carbon atoms present in one molecule of Z. Table 6.1 | type of hybridisation | sp | sp² | sp³ | | :--- | :--- | :--- | :--- | | number of carbon atoms | | | | (b) Z can undergo different reactions, as shown in Fig. 6.1. Fig. 6.1 (i) Name the two types of reaction occurring in reaction 7 in Fig. 6.1. ... and ... [1] (ii) Draw the structures of the organic products of reactions 7, 8 and 9 in Fig. 6.1. [4]
(c) Compound Z is dissolved in D$_2$O and analysed by carbon-13 NMR and proton (^1H) NMR spectroscopy.
(i) Predict the number of peaks in the carbon-13 NMR spectrum of Z.
(ii) The proton (^1H) NMR spectrum of Z in D$_2$O gives three peaks for the proton environments, labelled a, b and c, as shown on Fig. 6.2.
Fig. 6.2
Complete Table 6.2 for the proton (^1H) NMRpectrum of Z in D$_2$O.
Table 6.2
| proton environment | a | b | c |
| :--- | :--- | :--- | :--- |
| name of splitting pattern | | | |
| chemical shift range, $\delta$/ppm | | | |
Table 6.3
| environment of proton | example | chemical shift range, $\delta$/ppm |
| :--- | :--- | : ---: |
| alkane | $-\text{CH}_3$, $-\text{CH}_2-$, >CH- | 0.9–1.7 |
| alkyl next to C=O | CH$_3$-C=O, $-\text{CH}_2$-C=O, >CH-C=O | 2.2–3.0 |
| alky7 Phenylmethanol and 4-methylphenol are isomers.
(a) Complete Table 7.1 to show the relative acidities of benzoic acid ($C_6H_5COOH$), phenylmethanol, 4-methylphenol and water.
Explain your answer.
Table 7.1
name of compound
most acidic
least acidic
explanation ...
[4]
(b) 4-methylphenol reacts readily with sodium.
Complete the equation for this reaction.
$$\text{OH} + \text{C}_6\text{H}_5\text{COOH}$$(c) Under certain conditions, ethane-1,2-diol, HOCH₂CH₂OH, reacts with propane-1,3-dioic acid, HOOCCH₂COOH, to form different organic products, as shown in Fig. 7.1. Fig. 7.1 (i) X does not react with Na metal. Draw the structure of the organic product X, C₅H₆O₄, shown in Fig. 7.1. [1] (ii) Reactions 10 and 11 in Fig. 7.1 are different types of reaction. Name the type of reaction for reaction 10 and for reaction 11. reaction 10 .... reaction 11 .... [1] (iii) Draw a section of polymer Y showing only one repeat unit. The new functional group formed should be displayed.
8 (a) Describe the difference in reactivity between ethanoyl chloride and chlorobenzene with water. Explain your answer. [2] (b) The structure of compound V is shown. (i) Name all the functional groups in V. [2] (ii) Deduce the number of possible optical isomers for V. [1] (iii) Suggest one reason, other than better biological activity and lower dosage required, why it is beneficial to synthesise a single optical isomer of V for use as a drug. [1]
(c) A sample of V is hydrolysed with an excess of hot aqueous alkali. The products are isolated from the reaction mixture at pH 12. Draw the structures of the two organic products of the complete alkaline hydrolysis of V in Fig. 8.1. Fig. 8.1 [3]
(d) A polypeptide formed from four amino acids, A, B, C and D, is completely hydrolysed and then analysed by gas–liquid chromatography.
The chromatogram produced is shown in Fig. 8.2.
The number above each peak represents the area under the peak.
The area under each peak is proportional to the mass of the respective amino acid in the mixture.
(i) Calculate the percentage by mass of amino acid $A$ in the original mixture.
$$\text{percentage by mass of amino acid } A = \dots$$
(ii) The retention time for amino acid $D$ is the longest.
Explain why $D$ has a longer retention time than the other amino acids $A$, $B$ and $C$.
[Total: 11]