科目：化学 Chemistry (9701)
年份：2016 春季
试卷：Paper 42
总页数：18
章节：19 Lattice energy, 20 Electrochemistry, 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
Answer all the questions in the spaces provided.
1. (a) Complete the diagrams to show the energies of the electrons in a carbon atom, a C$^+$ ion and a C$^{-}$ ion.
(b) One of the simple molecular allotropes of carbon is buckminsterfullerene, $C_{60}$.
(i) What is the hybridisation of the carbon atoms in $C_{60}$?
[1]
(ii) $C_{60}$ reacts with an excess of hydrogen to form a single product, $C_{60}H_x$. Using your answer to (i), suggest a suitable value for $x$.
[1](c) Methylbenzene can undergo different reactions to form the products shown below. (i) Give the reagents and conditions for these two reactions. reaction 1 ... reaction 2 ... [2] (ii) Name the mechanism of reaction 1. ... [1] (iii) Draw the structure of the product obtained if reaction 1 is carried out using an excess of chlorine. [Total: 8]
2 (a) Calcium metal reacts with chlorine gas to form calcium chloride, CaCl$_2$.
(i) Write an equation, including state symbols, to represent the lattice energy of calcium chloride, CaCl$_2$.
[1]
(ii) Complete a fully labelled Born-Haber cycle that could be used to calculate the lattice energy, $\Delta H_{\text{latt}}^{\circ}$, for calcium chloride.
Ca(s) + Cl$_2$(g)
$\Delta H_{\text{f}}^{\circ}$
CaCl$_2$(s)
[2]
(iii) Use your answer to (ii) and the following data, together with relevant data from the Data Booklet, to calculate a value for $\Delta H_{\text{latt}}^\circ$ for calcium chloride.
| standard enthalpy change of formation of CaCl$_2$(s), $\Delta H_{\text{f}}^{\circs}$ | $-796 \text{ kJ mol}^{-1}$ |
| :--- | :--- |
| standard enthalpy change of atomisation of Ca(s), $\Delta H(c) The table shows four reactions.
(i) For each reaction, predict the sign of the entropy change, $\Delta S^\circ$. If you predict no entropy change, write ‘no change’ in the table below. The first one has been done for you.
| reaction | sign of $\Delta S^\circ$ |
| :---: | :---: |
| CO(g) + O$_2$(g) → CO$_2$(g) | negative |
| Mg(s) + $\frac{1}{2}$O$_2$(g) → MgO(s) | |
| CuSO$_4$(s) + 5H$_2$O(l) → CuSO$_4\cdot5H_5$O(s) | |
| NaHCO$_3$(s) + H$^+$(aq) → Na$^+$(aq) + CO$_2$(g) + H$_2$O(l) | |
(ii) Explain why the entropy change for the first process is negative.
[1]
(d) Calculate the standard entropy change, $\Delta S^\circs$, for this reaction.
$$N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$$
Standard entropies, $S^\circ$, in JK$^{-1}$mol$^{-1}$ are given.
| N$_2$(g) | H$_2$(g) | NH$_3$(g)3. (a) Complete the electronic structures of the following species.
Co [Ar] ..... [2]
Co$^{2+}$ [Ar] ..... [2]
(b) In an isolated transition metal atom the five d orbitals have the same energy. When a transition metal ion forms a tetrahedral complex the d orbitals are split into two groups of different energies.
Complete an orbital energy diagram to show this, indicating the number of orbitals in each group.
(c) Cobalt(II) forms a six co-ordinate complex containing three water molecules and three chloride ions.
(i) Write the formula of this complex showing the overall charge, if appropriate.
[1]
(ii) Explain, with the aid of diagrams, how many isomers of the complex in (i) exist.
[2]
(d) Platinum(II) forms a four co-ordinate complex containing two ammoni(ii) This complex exists as two isomers.
Draw the structure of these isomers and give their names.
(iii) One of the isomers in (ii) is an important anticancer drug.
State which isomer this is and explain why this isomer is effective.
isomer ...
reason ...
(e) Transition metal ions often exist as hexa-aqua complexes in aqueous solution. The reactions which involve ligand exchange are reversible.
$$[\text{Cu}(\text{H}_2\text{O})_6]^{2+} + 4\text{NH}_3 \rightleftharpoons [\text{Cu}(\text{NH}_3)_4(\text{H}_2\text{O})_{2}]^{2+} + 4\text{H}_2\text{O}$$
(i) Write an expression for the stability constant, $K_{\text{stab}}$, for this equilibrium. Give its units.
$$K_{\text{stab}} =$$
units = ...
(ii) The numerical value for $K_{\text{stab}}$ for this equilibrium at 298 K is $1.20 \times 10^{4 (a) Ethanal, CH$_3$CHO, dimerises in alkaline solution according to the following equation.
$$2\text{CH}_3\text{CHO} \rightarrow \text{CH}_3\text{CH(OH)}\text{CH}_2\text{CHO}$$
The initial rate of this reaction was measured, starting with different concentrations of CH$_3$CHO and OH$. The following results were obtained.
| [CH$_3$CHO]/mol dm$^{-3}$ | [OH]$^{-}$/mol dm$^{-3}$ | initial rate of reaction (relative values) |
| :--- | :--- | :--- |
| 0.10 | 0.015 | 1 |
| 0.20 | 0.015 | $2$ |
| 0.40 | 0.030 | $8$ |
(i) Deduce the order of the reaction with respect to CH$_3$CHO.
[1]
(ii) Deduce the order of the reactionwith respect to OH$^{-}$.
[1]
(iii) State the overall rate equation for this reaction.
rate = ..... [1]
(iv) State the units for the rate constant, $k$.
[1]
(v) Calcu(b) (i) A three-step mechanism has been proposed for the reaction in (a).
step 1
$$\text{CH}_3\text{-C}\overset{\ddot{\cdot}}{\underset{\cdot}{O}} + \text{OH} \rightleftharpoons \text{CH}_2\text{-C}\overset{\ddot}{\underset{\cdot}{O}} + H_2\text{O}$$
step 2
$$\text{CH}_3\text{:C}\overset{\ddot{\cdot}}{O} + \text{CH}_2\text{:C}\overset{\ddot}{\underingutilde}{O} \rightarrow \text{CH}_3\text{:C}\text{-C}\overset{\ddot{\circ}}{O} + \text{CH}_3\text{:C}-\text{CH}_2\text{:C}\text{-C}\oversets{\ddot{\circ}}{O}$$
step 3
$$\text{CH}_3\text:-\text{C}\text{-CH}_2\text{:C}\overset {\ddot{\circ}}{O} + H_2\text{O} \rightarrow \text{CH}_{3}\text:-\text{C}\text{-CH}_{2}\text{:C}\overset{\ddot{\circe}{O}}{+ \ddot{\circ}O}$$
Using your rate equation in (iii), predict which is the rate-determining st5 Some reactions of chromium ions are shown below.
$$\text{[Cr(H}_2\text{O})_6]^{2+}(\text{aq}) \xrightarrow[\text{metal} + \text{H}_2\text{SO}_4]{\text{reaction 1}} \quad \text{[Cr(H}_2\text{ O})_6]^{3+}(\text{aq}) \xrightwardarrow[\text{reaction 2}]{\text{Cr}_2\text{O}_7^{2-}(\text{aq})} \quad \text{H}_3\text{O}^+( \text{aq}) \quad \text{reaction 3} \quad \text{OH}^-( \text{aq}) \quad \text {CrO}_4^{2-}(\text{aq})
(a) (i) Use the Data Booklet to suggest a suitable metal to carry out reaction 1.
[1]
(ii) Use $E^\circ$ values to explain your answer to (i) by calculating the $E^\circ_{\text{cell}}$.
[2]
(b) A student suggested that reaction 2 could be carried out using acidified hydrogen peroxide solution.
Use the Data Booklet to show whether or not this reaction is feasible.
[2]
(c) E(d) The student used an acidified solution of Cr$_2$O$_7^{2-}$ (aq) to electroplate a steel box with chromium metal.
Calculate how long it would take for a current of 0.125A to deposit 0.0312g of chromium metal.
time = ..... [3]
[Total: 10]6 Two elements, $V$ and $W$, are in adjacent groups in the Periodic Table.
$V$ reacts with oxygen to form an acidic gas, $X$. $V$ forms an anion with formula $VO_{m}^{-}$.
$W$ reacts with oxygen to form an acidIC gas, $Y$. $W$ forms an anion with formula $WO_{n}^{2-}$.
A solution of $WO_{n}^{2-}$ forms a white precipitate with Ba$^{2+}$(aq) but shows no visible reaction with Mg$^{2+}$(aq).
(a) Complete the table below.
| identity or value |
|--------------------|
| $V$ |
| $X$ |
| $m$ |
| $W$ |
| $Y$ |
| $n$ |
[3]
(b) By referring to enthalpy changes, explain why $WO_{n}^{2-}$ formsa white precipitate with Ba$^{2+}$(aq) but shows no visible reaction with Mg${}^{2+}$.
[Total: 6]Question 7 starts on the next page.
7 (a) (i) State and explain the relative acidities of ethanol and phenol.
(ii) In the table below, give the reaction conditions for the formation of organic products D and E and draw their structures.
$$\text{Chemical structure}$$
$D \rightarrow \text{HNO}_3 \rightarrow \text{OH} \rightarrow \text{Br}_2 \rightarrow E$
phenol
| reagent | conditions | structure |
| :--- | :---: | :---: |
| $HNO_3$ | dilute, 5°C | D |
| $\text{Br}_2$ | | E |
(iii) Name the mechanism of the reaction forming compound E.
[1]
(b) (i) Phenylamine reacts with aqueous bromine to give compound F. Describe the appearance of compound F.
[1]
(ii) Phenylamine reacts with nitrous acid to form a diazonium salt. State the conditions for this reaction.
[1](iii) The diazonium salt in (ii) reacts with an alkaline solution of phenol to produce a coloured compound, G.
Draw the structure of G.
(c) Compound H is a primary amine which has three peaks in its carbon-13 NMR spectrum.
$$\text{H}_3\text{C} \longrightarrow \text{CH}_2 \longrightarrow \text{C} \longrightarrow \text{\text{CH}_2} \longrightarrow \text{CH_3}$$
compound H
(i) An isomer of H is another primary amine J which also has three peaks in its carbon-15 NMR spectrum.
Use this information to suggest the structure of J.
(ii) Another isomer of H is the tertiary amine K. It has three peaks in its proton NMR spectrum. One of the peaks is a doublet.
$$\text{H}_3\textC \longrightarrow \text{N} \longrightarrow \text{CH} \longrightarrow \text{CH}_{3}$$
K
Circle the protons responsibl8 Acebutolol is a drug that can be used to lower blood pressure. (a) Give the full name of the circled functional groups labelled P, Q and R in acebutolol. P .... Q .... R .... (b) On the diagram of acebutolol below, draw a circle around any chiral carbon atoms. (c) On warming with dilute hydrochloric acid, acebutolol splits to form two molecules. (i) Draw a line through the bond broken by heating with dilute hydrochloric acid. [1] (ii) Draw the structure of the smaller molecule produced by this reaction. [1]
(d) Suggest what would be observed when acebutolol reacts with the following reagents. If no reaction would take place, write ‘none’ in the table below. | reagent | observation | | :--- | :--- | | alkaline iodine solution | | | universal indicator solution | | | 2,4-dinitrophenylhydrazine | | | Tollens’ reagent | | (e) Butanoic acid can be reduced to form compound N. Compound N reacts with sodium. (i) Suggest a suitable reducing agent for this reaction. [1] (ii) Draw the skeletal formula of the isomer of N that exists as a pair of optical isomers. [1] (iii) Another isomer of N does not react with acidified dichromate(VI) solution but does react with sodium. Draw the structure of this isomer. [Total: 12]
9. (a) (i) Name an example of a synthetic polyester and a synthetic polyamide. polyester ... [1] polyamide ... [1] (ii) Polyesters and polyamides are formed by condensation reactions. Name a molecule which is commonly eliminated in such reactions. (b) (i) The table shows the repeat units of a number of polymers. Place a tick ($\checkmark$) against the ones which are biodegradable. | polymer | repeat unit | biodegradable | | :--- | :---: | :---: | | A |  | | | B |  | | C | | | D | | (ii) Draw the structures of two monomers used to form polymer B.
(c) A section of polypeptide was hydrolysed and the following amino acids identified. | amino acid | formula | | :--- | :--- | | T | CH₃CH(NH₂)CO₂H | | U | C₆H₅CH₂CH(NH₂)CO₂ H | | V | H₂N(CH₂)₄CH(NH₂)CO₂_H | (i) Which of the amino acids $T$, $U$ or $V$ has the highest pH in aqueous solution? Explain why. amino acid ..... [1] (ii) State how many different dipeptides could be formed from a reaction mixture consisting of amino acids $T$ and $U$. [1] (iii) Polypeptides contain a high proportion of carbon and hydrogen in their structures, yet many are soluble in water. By referring to the structure of a polypeptide, explain why. [2] [Total: 10]