科目：化学 Chemistry (9701)
年份：2019 夏季
试卷：Paper 41
总页数：19
章节：19 Lattice energy, 20 Electrochemistry, 21 Further aspects of equilibria, 22 Reaction kinetics, 24 Transition elements, 25 Benzene and its compounds, 26 Carboxylic acids and their derivatives, 27 Organic nitrogen compounds, 28 Polymerisation, 30 Analytical chemistry
Answer all the questions in the spaces provided.
1. (a) Aqueous solutions of copper(II) salts contain the blue-coloured $[\text{Cu(H}_2\text{O})_6]^{2+}$ complex ion. Separate portions of this blue solution react with aqueous sodium hydroxide and with concentrated hydrochloric acid.
Give the following information for each of these reactions.
- reaction with aqueous sodium hydroxide
- ionic equation ...
- type of reaction ...
- colour and state of the copper-containing product ...
- reaction with concentrated hydrochloric acid
- ionic equation ...
-type of reaction ...
- colour and state ofthe copper-containing product ..... [6]
(b) Chloride ions can be identified using aqueous silver nitrate, $\text{AgNO}_3(\text{aq})$.
$$\text{Ag}^+( \text{aq}) + \text{Cl}^- (\text{aq}) \2 (a) Group 2 nitrates decompose when heated. Write an equation for the decomposition of strontium nitrate. [1] (b) Describe and explain how the thermal stability of Group 2 nitrates changes with increasing atomic number. [3] (c) The variation in the thermal stability of Group 2 amides is similar to that of Group 2 nitrates. (i) Suggest whether calcium amide, Ca(NH$_2$)$_2$, will decompose more or less readily than barium amide, Ba(NH$_2$)$_2$. Explain your answer. [1] (ii) Ba(NH$_2$)$_2$ decomposes when heated to form barium nitride, Ba$_3$N$_2$, and ammonia as the only products. Write an equation for this reaction. [1] (d) Ba(NH$_2$)$_�$ contains the NH$_2^-$ ion. Predict the bond angle of NH$_2^-$. Explain your answer using the qualitative model of electron-pair repulsion.
3 Chlorate(V) ions are powerful oxidising agents.
(a) The reduction of chlorate(V) ions, $ClO_3^-$, with SO$_2$ forms chlorine dioxide, $ClO_2$, and sulfate ions, $SO_4^{2-}$, as the only products.
Construct an equation for this reaction.
[1]
(b) (i) Chlorine dioxide, $ClO_2$, disproportionates with hydroxide ions, OH$^{-}$(aq), to form a mixture of $ClO_2^-$ and $ClO_3^-$ ions.
$$2ClO_2 + 2OH^- \rightarrow ClO_2^- + ClO_3^- + H_2O$$
Explain, using this reaction as an example, what is meant by disproportionation.
[1]
(ii) Deduce the ionic half-equations for the reaction in (b)(i).
[2]
(c) A lithium-iodine electrochemical cell can be used to generate electricity for a heart pacemaker. The cell consists of a lithium electrode and an inert electrode immersed in body fluids. When cur(iii) A current of $2.5 \times 10^{-5} \text{A}$ is drawn from this cell.
Calculate the time taken for $0.10\text{g}$ of lithium electrode to be used up. Assume the current remains constant throughout this period.
time = ..... s [3]
[Total: 10]4 (a) Sketches of the shapes of some atomic orbitals are shown.
Identify the type of orbital, s, p, or d.
[1]
(b) Cadmium forms the two ions, Cd$_{2}^{2+}$ and Cd$^{2+}$. The electronic configuration of cadmium in these ions is shown.
- [Kr] $4d^{10}5s^1$
- [Kr] $4d^{^{10}}$
Use this information to explain why cadmium is **not** a transition element.
[1]
(c) Methylamine, CH$_3$NH$_2$, is a monodentate ligand.
(i) State what is meant by the term *monodentate* in this context.
[1]In the presence of aqueous methylamine, $[\text{Cd}(\text{H}_2\text{O})_6]^{2+}$ reacts to form a mixture of two isomeric octahedral complexes.
$$\text{equilibrium 1} \quad [\text{Cd}(\text{H}_�\text{O})_6]^{2}+4\text{CH}_3\text{NH}_2 \rightleftharpoons [\text{Cd}(\text{CH}_3\text{NH}_2)_4(\text{H}_�\text{O})_{2}]^{2}+4\text{H}_2\text{O} \quad \Delta H^\circ_{\text{r}} = -57 \text{ kJ mol}^{-1}$$
(ii) Complete the three-dimensional diagrams to show the isomers of $[\text{Cd}(\text{CH}_�\text{NH}_2)_4(\text {H}_�\text{O})_2]^{2+}$. Use L to represent $\text{CH}_3\text{NH}_$ in your diagrams.
[2]
(d) (i) State what is meant by the term stability constant.
[1]
(ii) Complete the table by placing one tick ($\checkmark$) in each row to suggest how increasing temperatEDTA$^{4-}$ is a polydentate ligand. When a solution of EDTA$^{4-}$ is added to $[\text{Cd(H}_2\text{O})_6]^{2+}$ a new complex $[\text{CdEDTA}]^{2-}$ is formed.
The values for the stability constants for two Cd$^{2+}$ complexes are shown.
| | $K_{\text{stab}}$ |
| :---: | :---: |
| $[\text{Cd(CH}_3\text{NH}_2)_4(\text{H}_2\text{O})_2]^{2+}$ | $4.0 \times 10^6$ |
| $[\text{CdEDTA}]^2-$ | $4.0 \times 1$$16$ |
(iii) A solution containing equal numbers of moles of CH$_3$NH$_2$ and EDTA is added to $[\text{Cd}(\text{H}_2\text{O})_{6}]^{2+}$. Predict which complex is formed in the larger amount. Explain your answer.
[1]
(e) Methylamine is a Brønsted-Lowry base.
Write an equation showing how methylamine dissolves in water to give an alkaline solution.
[1]
(f) Methylamine is a useful reage5 (a) Chlorate(I) ions undergo the following reaction under aqueous conditions.
$$2\text{NH}_3 + \text{ClO}^- \rightarrow \text{N}_2\text{H}_4 + \text{Cl}^- + \text{H}_2\text{O}$$
A series of experiments was carried out at different concentrations of $\text{ClO}^-$ and $\text{NH}_3$.
The table shows the results obtained.
| experiment | $[\text{ClO}^-] / \text{mol dm}^{-3}$ | $[\text{NH}_3] / \text{mol dm}^{−3}$ | initial rate / mol dm$^{-3}$ s$^{-1}$ |
| :--- | :---: | :---: | :---: |
| 1 | 0.200 | 0.100 | 0.256 |
| 2 | 0.400 | 0.200 | 2.05 |
| 3 | 0.400 | 0.400 | 8.20 |
(i) Use the data in the table to determine the order with respect to each reactant, $\text{ClO}^-$ and $\mathrm{NH}_3$.
Show your reasoning.
[2]
(ii) Write the rate equation for this reaction.
rate = ..... [1]
((iv) On the axes sketch a graph to show how the value of $k$ changes as temperature is increased.
(b) In another experiment, the reaction between chlorate(I) ions and iodide ions in aqueous alkali was investigated.
A solution of iodide ions in aqueous alkaline was added to a large excess of chlorate(I) ions and $[I^-]$ was measured at regular intervals.
(i) Describe how the results of this experiment can be used to confirm that the reaction is first-order with respect to $[I^-]$.
... [2]
A three-step mechanism for this reaction is shown.
step 1 $\text{ClO}^-$ + $\text{H}_2\text{O} \rightarrow \text{HClO}$ + $\text{OH}^-$
step 2 $\text{I}^-$ + $\text{HClO} \rightarrow \text{HIO}$ + $\text{Cl}^-$
step 3 $\text{HIO}$ + $\text{OH}^-$ $\rightarrow \text{H}_2\text{O}$ + $\text{IO}^-$
(i6 (a) Complete the table by placing one tick ($\checkmark$) in each row to indicate the sign of each type of energy change under standard conditions.
| energy change | always positive | always negative | either negative or positive |
| :---: | :---: | :---: | :---
| bond energy | | | |
| enthalpy change of formation | | | |
(b) Explain what is meant by the term *enthalpy change of atomisation*.
[1]
(c) The overall reaction for the atomisation of liquid bromine molecules, Br$_2$(l), is shown.
$$\text{Br}_2(\text{l}) \rightarrow 2\text{Br}(\text{g})$$
This happens via a two-step process.
- Construct a labelled energy cycle to represent this atomisation process, including state symbols.
- Use your cycle and relevant data from the Data Booklet to calculate the enthalpy change of vaporis(e) (i) Explain what is meant by the term enthalpy change of hydration.
[1]
(ii) Suggest why the enthalpy change of hydration of Br$^{-}$(g) is more exothermic than that of I$^{-}$(g).
[2]
[Total: 9]7 (a) Benzene can be converted into cyclohexane.
(i) For this reaction name the type of reaction and identify the reagent and conditions needed.
type of reaction ...
reagent and conditions ..... [2]
(ii) State the bond angles in benzene and cyclohexane.
bond angle in benzene ... bond angle in cyclohexane ...
Explain your answers.
[2]
(b) When benzene reacts with SO$_3$, benzenesulfonic acid is produced.
The mechanism of this reaction is similar to that of the nitration of benzene. Concentrated H$_2$SO$_4$ is used in an initial step to generate the SO$_3$H$^+$ electrophile as shown.
$$\text{SO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{SO}_3\text{H}^+ + \text{HSO}_4^-$$
(i) Draw a mechanism for the reaction of benzene with SO$_3$H$^+$ ions. Include all necessary curly arrows and ch(c) 3-dodecylbenzenesulfonic acid can be prepared from benzenesulfonic acid.
Suggest the reagents and conditions and name the mechanism for this reaction.
reagents and conditions ...
mechanism ... [2]
(d) When concentrated sulfuric acid is added to water, dissociation takes place in two stages.
stage 1 $H_2SO_4 \rightleftharpoons H^+ + HSO_4^-$
stage 2 $HSO_4^- \rightleftharpoons H^* + SO_4^{2-}$ $K_{a2} = 1.0 \times 10^{-2} \text{ mol dm}^{-3}$
$K_{a2}$ is the acid dissociation constant for stage 2.
(i) Write the expression for the acid dissociation constant $K_{a2}$.
$$K_{a2} =$$
[1]
(ii) $H_2SO_4$ is considered a strong acid whereas $HSO_4^-$ is considered a weak acid.
Suggest how the magnitude of the acid dissociation constant for stage 1 compares to $K_{a2}$.
[1]
(e) Ben8 (a) The mass spectrum of compound X, C$_5$H$_{10}$O$_2$, is recorded.
The peak heights of the M and M+1 peaks are 22.65 and 1.25 respectively.
(i) Use these data to show that there are five carbon atoms present in one molecule of X.
Show your working.
[1]
(ii) The mass spectrum has a peak at $m/e = 57$.
Complete the equation to show the fragmentation of X to produce this peak.
$$\text{C}_5\text{H}_{10}\text{O}_2^+ \rightarrow + \dots$$
[2]
(b) State the use of TMS and CDCl$_3$ in NMR spectroscopy.
- TMS ...
- CDCl$_3$ ... [1](c) The proton NMR spectrum of compound X, C$_5$H$_{10}$O$_2$, is shown.
(i) By considering both the relative peak areas and their $\delta$ values, use the Data Booklet to
- deduce the part of the molecule that produces the peak at $\delta 2.2$,
- deduce the part of the molecule thatProduces the peaks at $\delta 1.2$ and $\delta 3.5$,
- deduce the part of the molecules that Produces the peak at $\delta 4.0$.
(ii) When reacted with aqueous alkaline iodine, X produces a yellow precipitate.
Use this information and your answers to (c)(i) to suggest a structure for X.(d) Compound $W$ is an ester with the molecular formula $C_5H_{10}O_2$.
The proton NMR spectrum of $W$ contains only two peaks.
The relative areas of these two peaks are in the ratio 9:1.
Suggest a structure for this ester, $W$.
[1]
(e) Compound $V$ is a carboxylic acid which contains a chiral centre. It also has the molecular formula $C_5H_{{10}O}_2$.
(i) Explain what is meant by the term chiral centre.
[1]
(ii) Suggest a structure for $V$.9 (a) Organochlorine compounds can undergo hydrolysis.
$$\text{R}-\text{Cl} + \text{H}_2\text{O} \rightarrow \text{R}-\text{OH} + \text{HCl}$$
State and explain the relative rates of hydrolysis of the following compounds.
$$\text{CH}_3\text{CH}_2\text{Cl} \quad \text{CH}_3\text{COCl} \quad \text{C}_6\text{H}_5\text{Cl}$$
[3]
(b) Epibatidine is a naturally occurring organochlorine compound.
(i) Epibatidine is a weak base.
State what is meant by the term *weak base*.
[1]
A molecule of epibatidine contains two nitrogen atoms, both of which can act as a base.
(ii) Epibatidine reacts with HCl(aq).
Complete the structure to suggest the product formed in this reaction.(c) Polyamides, such as nylon-6, can be prepared from a monomer that contains both an amine and an acyl chloride functional group.
$$\text{nylon-6 monomer}$$
(i) When the nylon-6 monomer is hydrolysed, bonds are broken and formed.
By considering the two steps in the mechanism of the reaction, complete the table by placing one tick ($\checkmark$) in each row to indicate the types of bonds broken and formed during the mechanism.
| | $\sigma$ bonds only | $\pi$ bonds only | both $\sigma$ and $\pi$ bonds |
| :--- | :---: | :---: | :---: |
| bonds broken | | | |
| bonds formed | | | |
(ii) Draw two repeat units of nylon-6. The amide bond should be shown fully displayed.
(d) An addition polymer made from two different alkene monomers is called a co-polymer. A section of a polyalkene co-pol(e) Explain why polyamides normally biodegrade more readily than polyalkenes. (f) The alkene phenylethene can be prepared from benzene in three steps. (i) Deduce the identity of compound H and draw its structure in the box. [1] (ii) Suggest reagents and conditions for each of the steps 1–3. step 1 ... step 2 ... step 3 ... [3] [Total: 15]