科目：化学 Chemistry (9701)
年份：2022 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 iodine is found naturally in compounds in many different oxidation states.
(a) Iodide ions, $I^-$, react with acidified $H_2O_2$(aq) to form iodine, $I_2$, and water. This reaction mixture is shaken with cyclohexane, $C_6H_{12}$, to extract the $I_2$. Cyclohexane is immiscible with water.
(i) Identify the role of $H_2O_2$(aq)在 its reaction with $I^-$ ions in acidic conditions.
Write an ionic equation for the reaction.
role ..... [2]
ionic equation ..... [2]
(ii) $15.0\text{cm}^3$ of $C_6H_{12}$ is shaken with $20.0\text{cm}^3$ of an aqueous solution containing $I_2$ until no further change is seen.
It is found that $0.390\text{g}$ of $I_2$ is extracted into the $C_6H_{12}$.
The partition coefficient of $I_2$ between $C_6H_{12}$ and water, $K_{\text{pc}}$, is 93.8.
Calculate the ma(b) The Group 1 iodides all form stable ionic lattices and are soluble in water.
(i) Define enthalpy change of solution.
[1]
(ii) Use the data in Table 1.1 to calculate the enthalpy change of solution of potassium iodide, KI.
Table 1.1
| process | enthalpy change, $\Delta H/kJmol^{-1}$ |
| :--- | :---:|
| $K^{+}(g) + I^{-}(g) \rightarrow KI(s)$ | –629 |
| $K^{+}(g) \rightarrow K^{+}(aq)$ | –322 |
| $I^{-}(g) \rightarrow I^{-}(aq)$ | –293 |
enthalpy change of solution = …… kJmol$^{-1}$ [1]
(iii) Suggest the trend in the magnitude of the lattice energies of the Group 1 iodides, LiI, NaI, KI.
Explain your answer.
[2](c) The concentration of Cu$^{2+}$(aq) in a solution can be determined by the reaction of Cu$^{2+}$ ions with I$^{-}$ ions.
$$\text{reaction 1} \quad 2\text{Cu}^{2+} + 4\text{I}^- \rightarrow 2\text{CuI} + \text{I}_2$$
The I$_2$ produced in reaction 1 is titrated against a solution containing thiosulfate ions, S$_2$O$_3$$^{2-}$, using a suitable indicator.
$$\text{reaction 2} \quad 2\text{S}_2\text{O}_3^{2-} + \text{I}_2 \rightarrow \text{S}_4\text{O}_6^{2-} + 2\text{I}^-$$
(i) A 25.0 cm$^3$ portion of a Cu$^{2+}$(aq) solution reacts with an excess of I$^{-}$(aq). The end-point of the titration occurs when 22.30 cm$^3$ of 0.150 mol dm$^{-3}$ S$_2$O$_3$$^{(2-)$$(aq)$ is added.
Calculate the concentration of Cu$^{2+}$(aq) in the original solution.
concentration of Cu$^{2+}$(aq)= ..... (d) The reaction of I$^{-}$ ions with persulfate ions, S$_2$O$_8^{2-}$, can be catalysed by Fe$^{3+}$ ions.
$$2\text{I}^{-} + \text{S}_2\text{O}_8^{2-} \rightarrow \text{I}_2 + 2\text{SO}_4^{2-}$$
Write equations to show how Fe$^{3+}$ catalyses this reaction.
[2]
(e) An orange precipitate of HgI$_2$ forms when Hg$^{2+}$ ions are added to KI(aq).
The solubility of HgI$_2$ at $25^{\circ}\text{C}$ is $1.00 \times 10^{-7}\text{ g dm}^{-3}$.
Calculate the solubility product, $K_{\text{sp}}$, of HgI$_2$.
Include units in your answer.
[$M_r$: $\text{HgI}_2$, 454.4)
value of $K_{\text{sp}} = .....$
units = ..... [3]
[Total: 19]2 Silicon is the second most abundant element by mass in the Earth’s crust.
(a) In industry, silicon is extracted from SiO$_2$ by reaction with carbon at over 2000 °C.
$$\text{reaction 1} \quad \text{SiO}_2(\text{s}) + 2\text{C}(\text{s}) \rightarrow \text{Si(l)} + 2\text{CO(g)}$$
(i) Explain why the entropy change, $\Delta S$, of reaction 1 is positive.
[1]
(ii) Reaction 1 is highly endothermic.
Suggest the effect of an increase in temperature on the feasibility of this reaction. Explain your answer.
[2]
(b) Silicon is purified by first heating it in a stream of HCl(g) to form SiHCl$_3$. The SiHCl$_3$ formed is then distilled to remove other impurities.
$$\text{reaction 2} \quad \text{Si(s)} + 3\text{HCl}(g) \rightarrow \text{SiHCl}_3(\text{g}) + \text{H}_2(\text{g})$$
(i) Table (ii) Reaction 3 is the reverse of reaction 2 and is used to obtain pure silicon.
$$\text{reaction 3} \quad \text{SiHCl}_3(\text{g}) + \text{H}_2(\text{g}) \rightarrow \text{Si(s)} + 3\text{HCl}(\text{g}) \quad \Delta H = +219.3 \text{kJ mol}^{-1}$$
Use this information and your answer to (b)(i) to calculate the temperature, in K, at which reaction 3 becomes feasible.
Show your working.
[If you were unable to answer (b)(i), you should use $\Delta S^e = -150 \text{ JK}^{-1} \text{mol}^{-1}$ for reaction 2. This is not the correct answer to (b)(i).]
temperature = ... K [2]
(c) Silicon can also be produced by electrolysis of SiO$_2$ dissolved in molten CaCl$_2$.
The relevant half-equation for the cathode is shown.
$$\text{SiO}_2 + 4\text{e}^- \rightarrow \text{Si} + 2\text{O}^{2-}$$
Cal3 Titanium is a transition element in Period 4. It is commonly found as TiO$_2$ in minerals.
(a) (i) Define transition element.
[1]
(ii) Identify two typical properties of transition elements.
1 ... [1]
2 ... [1]
(b) The TiO$_2^+$ ion forms when TiO$_2$ reacts with an excess of sulfuric acid.
TiO$_2^+$ can be reduced by zinc metal in acidic conditions to form a purple solution containing Ti$^{3+}$(aq).
(i) TiO$_2^+$(aq) is a colourless ion.
Suggest why.
[2]
(ii) Give the electronic configuration of an isolated Ti$^{3+}$ ion.
1s$^2$ ... [1]
(iii) Write an ionic equation for the reduction of TiO$_2^+$ by zinc metal in acidic conditions.
[1](c) Acidified Ti$^{3+}$(aq) reacts with oxygen dissolved in water as shown.
$$4\text{Ti}^{3+} + \text{O}_2 + 2\text{H}_2\text{O} \rightarrow 4\text{TiO}^{2+} + 4\text{H}^+ \quad \Delta G^\circ = -436.1\,\text{kJ mol}^{-1}$$
The standard reduction potential, $E^\circ$, of $\text{O}_2 + 4\text{H}^+ + 4\text{e}^-$ $\rightleftharpoons$ $2\text{H}_2\text{O}$ is $+1.23\,\text{V}$.
(i) Calculate the standard reduction potential, $E^\circ$ in V, of the TiO$^{2+}$(aq)/Ti$^{3+}$(aq) half-cell. Show your working.
$$E^\circ = \dots\dots\dots\dots\mathrm{V} \quad [3]$$
(ii) When aqueous citrate ions, C$_6$H$_5$O$_7$$^{3-}$, are added to Ti$^{3+}$(aq), the [Ti(C$_6$H$_5$O$_七)$_2]$^{3-}$(aq) complex forms.
Explain, in terms of d-orbitals, why Ti$^{3+}$ is able to form complex ions.
[1]
(iii) Acid(d) Some reactions of TiO$_2$ are shown in Fig. 3.1.
The anion, acac$, is a bidentate ligand.
$$\text{TiO}_2 \xrightarrow{\text{Cl}^-} \text{TiCl}_4 \xrightarrow{\text{acac}^-} \text{Ti(acac)}_2\text{Cl}_2$$
Fig. 3.1
(i) The titanium ions in $\text{TiF}_6^{2-}$ and $\text{Ti(acac)}_2\text{Cl}_2$ have a coordination number of 6.
State what is meant by coordination number.
[1]
(ii) Write an equation for the formation of $\text{TiF}_6^{2-$ from $\text{TiO}_2$.
[1]
(iii) State what is meant by bidentate ligand.
[2](iv) Ti(acac)$_2$Cl$_2$ shows both optical and geometrical (cis/trans) isomerism. Ti(acac)$_2$Cl$_�$ exists as three stereoisomers. The structure of one stereoisomer of Ti(acac)$_2$Cl $_2$ is shown in Fig. 3.2.  Fig. 3.2 Complete the structures of the other two stereoisomers of Ti(acac)$_2$ Cl$_2$.   (v) The acac$^-$ anion is symmetrical. Deduce which, if any, of stereoisomers 1, 2 and 3 in (d)(iv) are polar. Explain your answer. [Total: 19]
4 Compounds F and J are shown in Fig. 4.1. (a) F and J both contain the arene functional group. (i) Identify the other functional groups in F and J. F: ... J: ..... [2] (ii) State the number of chiral centres in a molecule of F and in a molecule of J. number of chiral centres in: F = ... J = ... [1] (b) A student proposes a multi-step synthesis of F from benzene, as shown in Table 4.1. (i) Complete Table 4.1 by providing relevant details of the reagents and conditions for steps 1 and 4, and the structure of product D. Table 4.1 | step | organic reactant | reagent(s) and conditions | organic product | | :--- | :--- | :--- | :--- | | 1 | | | | | 2 | | concentrated HNO₃ and concentrated H₂SO₄ | D | | 3 | D | hot alkaline KMnO₄ then dilute H₂SO₄ | E | | 4 | | | F |
(ii) In a second multi-step synthesis, the student changes the order in which the reagents and conditions are used. The reaction scheme is shown in Fig. 4.2. G is the major product of this synthesis. Fig. 4.2 Draw the structure of G. Explain why G is the major product of the synthesis rather than E.
(c) J reacts under suitable conditions with NaOH(aq). After acidification of the reaction mixture, compounds K and L form.  (i) Give the molecular formula of L. [1] (ii) State the two types of reaction that occur when J reacts with NaOH(aq). 1 ... [2] (d) K can also be synthesised from phenol, C$_6$H$_5$OH. Fig. 4.4 shows several reactions of phenol. 
(i) Write an equation for the formation of M in reaction 1.
(ii) Draw N, the product of reaction 2.
(iii) Explain why phenol is a weaker acid than K.
(e) Phenol and benzene both react with nitric acid, as shown in Fig. 4.5.
$$\text{OH} \xrightarrow{\text{dilute HNO}_3} \text{Chemical structure}$$
$$\text{concentrated HNO}_3 \xrightarrow{\text{concentrated H}_2\text{SO}_4} \text{Chemical structure}$$5 2-Chloropropanoic acid, CH$_3$CHClCOOH, is used in many chemical syntheses. (a) (i) An equilibrium is set up when CH$_3$CHClCOOH is added to water. Write the equation for this equilibrium. (ii) 0.150 mol of CH$_3$CHClCOOH dissolves in 250 cm$^3$ of distilled water to produce a solution of pH 1.51. Calculate the $pK_a$ of CH$_3$CHClCOOH. $$pK_a = \dots\dots\dots\dots\quad [2]$$ (iii) An equal concentration of aqueous propanoic acid has pH 2.55. Explain the difference in the pH of solutions of equal concentration of CH$_3$CHClCOOH and propanoic acid. (b) When CH$_3$CHClCOOH reacts with aqueous NH$_3$, alanine forms. Fig. 5.1 Alanine is an amino acid. Its isoelectric point is 6.1. (i) State what is meant by isoelectric point. [1]
(ii) Give the structural formula of alanine at pH 2. (iii) Alanine exists as a pair of optical isomers. The structure of one optical isomer is shown in Fig. 5.2. Draw the three-dimensional structure of the other optical isomer of alanine. Fig. 5.2 (iv) Polymer C forms from the reaction between alanine and 4-aminobutanoic acid, $H_2N(CH_2)_3COOH$. Draw a repeat unit of C. The functional group formed should be displayed. (v) State the type of polymerisation shown in (b)(iv). (vi) Scientists are investigating C as a replacement for poly(propene) in packaging. Suggest an advantage of using C instead of poly(propene).
(c) A student studies the reaction of CH$_3$CHClCOOH with aqueous NH$_3$ to determine the reaction mechanism.
The student finds that when CH$_3$CHClCOOH and NH$_3$ are added in a 1:1 stoichiometric ratio, the conjugate acid and base of the reactants are quickly formed.
$$\text{reaction 1} \quad \text{CH}_3\text{CHClCOOH} + \text{NH}_3 \rightarrow \text{CH}_3\text{CHlCOO}^- + \text{NH}_4^+$$
(i) Identify the conjugate acid–base pairs in reaction 1.
conjugate acid–base pair I ... and ...
conjugate acid–base pair II ... and ..... [1]
In an excess of NH$_3$, CH$_3$CHClCOO$^{-}$ undergoes a nucleophilic substitution reaction.
$$\text{reaction 2} \quad \text{CH}_3\mathrm{CHlCOO}^{-} + \text{NH}_3 \to \text{CH}_3\mathrm{C}\left(\mathrm{NH}_2\right)\mathrm{COO}^{-} + \text{H}^+ + \text{Cl}^-(ii) Use the graph in Fig. 5.3 to show that reaction 2 is first order with respect to $[\text{CH}_3\text{CHClCOO}^-]$.
[2]
(iii) Explain why a large excess of $\text{NH}_3$ needs to be used in order to obtain the results in Fig. 5.3.
[1]
(iv) The student measures the effect of changing the concentration of $\text{NH}_3$ on the rate of reaction 2. Table 5.1 shows the results obtained.
Table 5.1
| experiment | $[\text{CH}_3\text{ChClCOO}^-] / \text{mol dm}^{-3}$ | $[\text{NH}_3] / \text{mol dm}^{−3}$ | initial rate of reaction / mol dm$^{-3}$ s$^{-1}$ |
| :--- | :---: | :---: | :---: |
| 1 | 0.00120 | 0.00300 | $1.47 \times 10^{-5}$ |
| 2 | 0.00120| 0.00450 | $2.21 \times 10^{-5}$ |
Use the information in Table 5.1 and in (c)(ii) to determine whether the nucleophilic substitution reac(v) Describe the effect of an increase in temperature on the rate of reaction of CH$_3$CHClCOO$^-$ and NH$_3$.
Explain your answer.
[2]
(vi) When an excess of CH$_3$CHClCOO$$^-$ is used, further substitution reactions occur. One product has the formula C$_6$H$_9$NO$_4^{2-}$.
Suggest the structure of C$_6$H$_9$NO $_4^{2-}$.
[1]
[Total: 21]6 Lidocaine is used as an anaesthetic. A synthesis of lidocaine is shown in Fig. 6.1. Fig. 6.1 (a) W can be formed by reacting HOCH$_2$COOH with an excess of SOCI$_2$. Write an equation for this reaction. [1] (b) After W and X have reacted together, an excess of CH$_3$COONa(aq) is added to the reaction mixture. Suggest why. [1]
(c) The reaction of W with X, reaction 1, follows an addition–elimination mechanism.
Complete the mechanism for the reaction of W with X.
Include all relevant curly arrows, lone pairs of electrons, charges and partial charges.
Use Ar–NH₂ to represent X.
$$\text{Ar} \longrightarrow \text{NH}_2$$
[4]
(d) (C₂H₅)₂NH reacts with Y in reaction 2.
Explain why (C₂H₅)�２NH can act as a nucleophile.
... [1](e) The purity of lidocaine can be checked using thin-layer chromatography. Ethyl ethanoate is used as the solvent. The $R_f$ values of X and lidocaine are given in Table 6.1. | compound | $R_f$ | | :--- | :--- | | X | 0.49 | | lidocaine | 0.71 | (i) Identify the substances used as the mobile and stationary phases in this thin-layer chromatography experiment. mobile phase ... stationary phase ... [1] (ii) Describe how an $R_f$ value can be calculated. ... [1] (iii) Suggest why the $R_f$ value for X is less than that for lidocaine. ... [1]
(f) The proton (1H) NMR spectrum of lidocaine is shown in Fig. 6.2.
Fig. 6.2
Table 6.2
| 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 | $CH_3-\text{Ar}, -CH_2-\text{Ar}, >CH-\text{Ar}$ | 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 | 9.0–13.0 |
| alkyl amine | R-NH-$-$ | 1.0–5.0 |
| aryl amine | Ar-NH$_2$ | 3.0–6.0 |
| amide | RCONHR | 5.0–12.0 |(i) Name the splitting patterns at $\delta 2.6$ and $\delta 1.1$.
$\delta 2.6 \ldots \delta 1.1 \ldots$
(ii) The relative peak area of the peaks at $\delta 3.0$ and $\delta 2.3$ is $1:3$ respectively.
Identify the protons in the ${}^{1}\text{H}$ NMR spectrum of lidocaine that are responsible for the peaks at the following chemical shift values.
$\delta 7.1$
$\delta 3.0$
$\delta 2.3$
(iii) Predict the number of peaks in the **carbon-13** ($^{13}\text{C}$) NMR spectrum of lidocaine.
[Total: 14]