科目：化学 Chemistry (9701)
年份：2018 春季
试卷：Paper 42
总页数：18
章节：19 Lattice energy, 20 Electrochemistry, 21 Further aspects of equilibria, 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) (i) State how the solubilities of the hydroxides of the Group 2 elements vary down the group.
[1]
(ii) Explain the factors that are responsible for this variation.
[3]
(b) The solubility of Sr(OH)$_2$ is $3.37 \times 10^{-2}$ mol dm$^{-3}$ at 0 °C.
(i) Write an expression for the solubility product of Sr(OH)$_2$.
$$K_{sp} =$$
[1]
(ii) Calculate the value of $K_{sp}$ at 0 °C. Include units in your answer.
$$K_{sp} = \text{units} =$$
[2](c) Metal peroxides contain the $^-O-O^-$ ion.
The peroxides of the Group 2 elements, MO$_2$, decompose on heating to produce a single gas and the solid oxide, MO, only.
(i) Write an equation for the thermal decomposition of strontium peroxide, SrO$_2$.
[1]
(ii) Suggest how the temperature at which thermal decomposition of MO$_2$ occurs varies down Group 2.
Explain your answer.
[3]
(d) (i) The ethanedioates of the Group 2 elements, MC$_2$O$_4$, decompose on heating to produce a mixture of two different gases and the solid oxide, MO, only.
Complete the equation for the thermal decomposition of barium ethanedioate.
$$\text{BaC}_2\text{O}_4 \rightarrow + +$$
[1]
(ii) Describe two observations you would make during the reaction when ethanedioic acid, H$_2$C$_2$O$_4$, is warmed with ac2 (a) Describe the trend in the reactivity of the halogens Cl$_2$, Br$_2$ and I$_2$ as oxidising agents. Explain this trend using values of $E^\circ$(X$_2$/X$^-$) from the Data Booklet.
[2]
(b) (i) Write an equation for the reaction between chlorine and water.
[1]
(ii) Use standard electrode potential, $E^\circ$, data from the Data Booklet to calculate the $E^\circ_{\text{cell}}$ for the following reaction.
$$\text{Cl}_2 + 2\text{OH}^- \rightleftharpoons \text{Cl}^- + \text{ClO}^- + \text{H}_2\text{O}$$
$$E^\circ_{\text{cell}} = \dots\dots\dots\dots\ V$$ [2]
(iii) The [OH]$^{-}$ was increased and the $E_{\text{cell}}$ was measured.
Indicate how the value of the $E_{\text{cell}}$ measured would compare to the $E^\circ_{\text{-cell}}$ calculated in (ii) by placing one tick ($\checkma(c) A half-equation involving bromate(V) ions, BrO$_3^-$, and bromide ions is shown.
$$\text{BrO}_3^-(\text{aq}) + 3\text{H}_2\text{O}(\text{l}) + 6\text{e}^- \rightleftharpoons \text{Br}^-(\text{aq}) + 6\text{OH}^-(\text{aq}) \quad E^\circ = +0.58\text{V}$$
(i) An alkaline solution of chlorate(I), ClO$_3^-$, can be used to oxidise bromide ions to bromate(V) ions.
Use the Data Booklet and the half-equation shown to write an equation for this reaction.
[1]
(ii) Calculate the $E^\circ_{\text{cell}}$ for the reaction in (i).
$$E^\circ_{\text{cell}} = \dots\dots\dots\dots\ V$$ [1]
(iii) When a concentrated solution of bromic(V) acid, HBrO$_3$, is warmed, it decomposes to form bromine, oxygen and water only.
Write an equation for this reaction. The use of oxidation numbers may be helpfu3 (a) Hydrogen cyanide, HCN, is a weak acid in aqueous solution.
$$\text{HCN(aq)} \rightleftharpoons \text{H}^+(\text{aq}) + \text{CN}^{-}(\text{aq}) \quad K_a = 6.2 \times 10^{-10} \text{mol dm}^{-3}$$
(i) Calculate the pH of $0.10\text{ mol dm}^{-3}$ HCN(aq).
$$\text{pH} = ...$$ [2]
(ii) Draw a ‘dot-and-cross’ diagram to represent the bonding in the hydrogen cyanide molecule. Show the outer shell electrons only.
[1]
(iii) State the hybridisation of the carbon and nitrogen atoms in hydrogen cyanide, and give the H–C–N bond angle.
hybridisation of C .....
hybridisation of N .....
H–C–N bond angle ..... [2]
(iv) Suggest structures for the organic products A and B in the following reactions. Assume that HCN reacts in a similar way to RCN.
$$\begin{array}{c}
\text{A} \\
\text{H}_2 (b) Adding a measured quantity of KCN to a solution of NiCl$_2$ produces the complex [Ni(CN)$_2$Cl$_2$]$^x$.
(i) Deduce the overall charge, $x$, on this complex.
$$x = \dots\dots\dots\dots\ldots\ldots\ldots\ldotp$$
The complex can exist as two separate isomers with the same geometry (shape) around the nickel ion.
(ii) State the type of isomerism shown by these isomers.
...[1]
(iii) If bromide ions are present in the solution, the complex [Ni(CN)$_2$-ClBr]$^x$ can form.
Assuming that [Ni(CN)$_2$-Cl Br]$^x$ has the same geometry as [Ni(CN)$_2$-Cl$_2$]$^x$, state the number of isomers of [Ni(CN)$_2$-Cl br]$^x$ that could exist, and draw their structures in the box.
- number of isomers of [Ni(Cn)$_2$-ClBr]$^x$
- structures of the isomers of [Ni(Cn)$_{2}$ClBr]$^x$
(c) An aqueous soluti4 (a) (i) State what is meant by the term partition coefficient.
Ammonia is soluble in both water and organic solvents.
An aqueous solution of ammonia is shaken with the immiscible organic solvent trichloromethane. The mixture is left to reach equilibrium.
Samples are taken from each layer and titrated with dilute hydrochloric acid.
- A 25.0 cm$^3$ sample from the trichloromethane layer requires 13.0 cm$^3$ of 0.100 mol dm$^{-3}$ HCl to reach the end-point.
- A 10.0 cm$^3$ sample from an aqueous layer requires 12.5 cm$^3$ of 0.0100 mol dm$^{-3}$$\text{HCl}$ to reach the end-point.
(ii) Calculate the partition coefficient, $K_{\text{partition}}$, of ammonia between trichloromethane and water.
$$K_{\text{partition}} = \dots$$
(iii) Butylamine, C$_4$H$_9$NH$_2$, is also soluble in both (b) (i) Explain why butylamine is basic. (ii) Write an equation to show butylamine reacting as a base. (iii) State how the basicity of butanamide, $C_3H_7CONH_2$, compares to that of butylamine. (iv) State a reagent for the conversion of butanamide into butylamine. [Total: 9]
5 (a) (i) Complete the electronic configuration of a chromium atom.
$$1s^2 2s^2 2p^6 3s^2$$ ... [1]
(ii) State the two highest oxidation states of chromium commonly seen in its compounds.
... [1]
(b) Six different compounds or complexes, H, J, K, L, M and N, are formed when an excess of aqueous NH$_3$, aqueous NaOH and concentrated aqueous HCl are separately added to separate solutions containing Cu$^{2+}$(aq) or Co$^{2+}$(aq).
| solution | reagent |
| :--- | :--- |
| an excess of NH$_3$(aq) | an excess of NaOH(aq) | an excess of concentrated HCl(aq) |
| Cu$^{2+}$(aq) | H | J | K |
| Co$^{2+}$(aq) | L | M | N |
(i) State the colours of the following compounds or complexes.
H ... [2]
K ... [2]
M ... [2]
(ii) Write the formulae of the following compounds or complexes.
L ... [2]
N 6 The apparatus shows a cell which can be used to determine a value of the Avogadro constant, L.
(a) (i) Name component X.
[1]
(ii) Suggest a suitable electrolyte Y.
[1]
(b) In an experiment, a current of 0.200A was passed through the cell for 40.0 minutes. The mass of the silver cathode increased by 0.500g.
The charge on the electron is $-1.60 \times 10^{-19}$ C.
Calculate the:
• number of moles of silver deposited on the cathode
• number of coulombs of charge passed
• number of electrons passed
• number of electrons needed to deposit 1 mol of silver at the cathode.
[3]
[Total: 5]7 (a) (i) Complete the equations to show the two types of polymerisation. Draw one repeat unit for each polymer. Include any other products.
- addition polymerisation
$$n\text{CH}_2 = \text{CHCH}_3(\text{g}) \rightarrow$$
- condensation polymerisation
$$n\text{HO}_2\text{CCH}_2\text{CO}_2\text{H}(\text{s}) + n\text{HOCH}_2\text{CH}_2\text{OH}(\text{l}) \rightarrow$$
[3]
(ii) Suggest the sign of the entropy changes, $\Delta S^\circ$, for each of the two types of polymerisation. Explain your answers.
- $\Delta S^\circ$ for addition polymerisation
....
- $\Delta S^\circ$ für condensation polymerisation
....
[2](b) An amide bond forms when a carboxylic acid reacts with an amine.
(i) Complete the equation by writing the products in the box.
$$\text{R}-\text{CO}_2\text{H} + \text{H}_2\text{N}-\text{R}' \rightarrow +$$
(ii) Use your answer to (i) to work out the bonds that are broken and the bonds that are formed during the reaction between a carboxylic acid and an amine.
- bonds that are broken
- bonds that are formed
(iii) Use bond energy values from the Data Booklet to calculate the enthalpy change, $\Delta H^\circ$, when one mole of amide bonds is formed in the reaction in (i).
$$\Delta H^\circ = \text{kJ}$$
(c) Amide bonds can also be formed by reacting acyl chlorides with amines.
The enthalpy change for this process, $\Delta H^\circ$, is $-6.00$ kJ mol$^{-1}$.
Calculate the minimum enThe repeat unit of the polyamide Kevlar is shown.
(d) The monomers of Kevlar, benzene-1,4-dioic acid and 1,4-diaminobenzene, can be synthesised as follows.
$$\begin{array}{ccc}
\text{reaction 1} & \text{reaction 2} & \text{1,4-diaminobenzene}
\end{array}$$
State the reagents and conditions needed for:
(i) reaction 1
[1]
(ii) reaction 2
[2]
(e) Kevlar is both strong and rigid.
Complete the table to identify two intermolecular forces and the groups involved which are responsible for these properties of Kevlar.Question 8 starts on the next page.
8 (a) Cumin is a spice used to flavour food. Two compounds responsible for its flavour are cuminaldehyde and cuminyl alcohol.
(i) Deduce the number of peaks that would be present in the $^{13}$C NMR spectrum of cuminyl alcohol.
number of peaks ... [1]
(ii) Identify two bonds that are responsible for the differences in the infra-red spectra of cuminaldehyde and cuminylcohol, and state their absorption ranges.
| | Absorption range in the infra-red spectrum / cm$^{-1}$ |
| :--- | :---:|
| bond responsible for the difference | cuminaldehyde | cuminyl alcohol |
| | | |
| | | |
[2](b) Cuminyl alcohol can be synthesised from benzene by the following route. (i) Suggest reagents and conditions for steps 1–4. step 1 ... step 2 ... step 3 ... step 4 ... [4] (ii) Name the mechanism of step 2 and state the type of reaction in step 4. mechanism of step 2 ... type of reaction in step 4 ... [2] [Total: 9]
9 (a) Two molecules of compound F react together under suitable conditions to form compound G. Some information about compounds F and G is given.
- The mass spectrum of F has a peak due to the molecular ion at $m/e = 106$, and a peak at $m/e = 107$ with an abundance 8% of the 106 peak.
- The mass spectrum of G has a peak due to the molecular ion at $$m/e = 212$$, and major peaks at $m/e = 91$ and $m/e = 105$.
- Both F and G contain oxygen and are neutral compounds which are insoluble in water.
- The $^1\text{H}$ NMR spectrum of F includes a singlet peak at $\delta = 10.0$ due to one proton.
- The $^1\text{H}$$\text{NMR}$ spectrum of G includes a singlet peak at $$\delta = 5.1$$ due to two protons.
- When G is heated with dilute sulfuric acid, benzoic acid, C$_6$H$_5$CO$_2$H, and phenylmet(vi) State the type of reaction that G undergoes when heated with dilute sulfuric acid. [1] (b) Describe and explain the relative acidities of benzoic acid, phenylmethanol and 4-methylphenol. benzoic acid phenylmethanol 4-methylphenol [3] (c) The ester 4-methylphenyl benzoate is used in the manufacture of perfumes. 4-methylphenyl benzoate Suggest a two-step route for the synthesis of 4-methylphenyl benzoate from 4-methylphenol and benzoic acid. Include reagents and conditions for each step, and the structure of the intermediate compound.