科目：化学 Chemistry (9701)
年份：2016 冬季
试卷：Paper 43
总页数：19
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. Copper is a transition element and has atomic number 29.
(a) Complete the electronic configuration for the copper atom and the copper ion in the +2 oxidation state.
• copper atom [Ar]
• copper ion in the +2 oxidation state [Ar]
(b) The following equilibrium exists between two complex ions of copper in the +2 oxidation state.
$$[\text{Cu}(\text{H}_2\text{O})_6]^{2+} + 4\text{Cl}^- \rightleftharpoons [\text{CuC}\text{l}_4]^{2-} + 6\text{H}_2\text{O}$$
(i) Name the type of reaction occurring here.
... [1]
(ii) State the colours of these two complex ions.
$$[\text{Cu}(\mathrm{H}_2\mathrm{O})_6]^{2+}$$
$$[\text{CuC}\text{l}_�]^{2-}$$
(iii) State the shape of the $[\text{C(ii) The table lists the values of stability constants for these two complexes.
$$\begin{array}{|c|c}
\text{Stability constant, } K_{\text{stab}} \\
[Cu(NH_3)_2(H_2O)_4]^{2+} & 7.94 \times 10^7 \\
[Cu(en)(H_2O)_4]^{2+}
\end{array}$$
What do these $K_{\text{stab}}$ values tell us about the relative positions of equilibria 1 and 2?
[1]
(d) Nickel forms the complex ion $$[\text{Ni}(en)_3]^{2+}$$ in which it is surrounded octahedrally by six nitrogen atoms.
(i) Name the type of stereoisomerism displayed by $$[\text{Ni}(en)_3](2+)$$.
[1]
(ii) Draw three-dimensional diagrams to show the two stereoisomers of $$[\text{Ni}(en)_3]{2+}$$.
[3]
(e) Ethane-1,2-diamine is a useful reagent in organic chemistry.
(i) Explain how the amino groups in ethane-1,2-diamine allow the molecule to act as a(f) (i) Under certain conditions, ethane-1,2-diamine reacts with ethanedioic acid, HO$_2$CCO$_2$H, to form the polymer Z. Draw the structure of this polymer, Z, showing two repeat units. [2] (ii) Name the type of reaction occurring during this polymerisation. [1] (iii) Polymer Z is an example of a biodegradable polymer. Name a polymer that is non-biodegradable. [1] [Total: 20]
2 (a) When copper(II) carbonate is heated strongly, it decomposes in a similar way to Group 2 carbonates.
Predict what would be observed when anhydrous copper(II) carbonate is heated.
[1]
(b) Describe and explain how the thermal stability of the Group 2 carbonates varies down the group.
[3]
(c) Calcium cyanamide, CaCN$_2$, can be used as a fertiliser.
(i) Complete the ‘dot-and-cross’ diagram for the cyanamide ion, CN$_2$^{2-}$.
Use the following key for the electrons.
- electrons from carbon
- electrons from nitrogen
- added electron(s) responsible for the overall negative charge
$$\text{CaCN}_2 \xrightarrow{\Delta} \text{N}_2\text{C}_2\text{N}_2$$
[2]
(ii) CaCN$_2$ decomposes readily on contact with water forming an insoluble white solid and ammonia only.
Suggest an equation fo3 The spontaneity (feasibility) of a chemical reaction depends on the standard Gibbs free energy change, $\Delta G^\circ$. This is related to the standard enthalpy and entropy changes by the equation shown.
$$\Delta G^\circ = \Delta H^\circ - T \Delta S^\circ$$
(a) State and explain whether the following processes will lead to an increase or decrease in entropy.
(i) the reaction of magnesium with hydrochloric acid
entropy change ..... [1]
explanation ..... [1]
(ii) solid potassium chloride dissolving in water
entropy change ..... [1]
(explanation ..... [1])
(iii) steam condensing to water
entropy change ..... [1](explanation ..... [1])
explanation ..... [1]
(b) Magnesium carbonate can be decomposed.
$$\text{MgCO}_3(s) \rightarrow \text{MgO}(s) + \text{CO}_2(g) \quad \Delta H^\(c) On heating, sodium hydrogencarbonate decomposes into sodium carbonate as shown.
$$2\text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s) + \text{CO}_2(g) + \text{H}_2\text{O}(g) \quad \Delta H^\circ = +130\,\text{kJ mol}^{-1} \\
\Delta S^\circ = +316\,\text{J mol}^{-1}\text{K}^{-1}$$
Calculate the **minimum** temperature at which this reaction becomes spontaneous (feasible). Show your working.
temperature = ..... K [2]
(d) The solubility of Group 2 sulfates decreases down the Group.
Explain this trend.
[Total: 11]4 (a) Cobalt is a transition element that forms complex ions with oxidation states +2 and +3. Explain what is meant by the term transition element.
[1]
(b) The following scheme shows some reactions of $[\text{Co}(\text{H}_2\text{O})_6]^{2+}$.
(i) State the formula of each of the following.
A ...
B ...
C ... [2]
(ii) State the colour of the following solutions.
$[\text{Co}(\text{H}_�\text{O})_6]^{2^+}$ ... solution of B ... solution of C ... [2]
(c) Define the term standard electrode potential.
... [2](d) An electrochemical cell was set up to measure the standard electrode potential, $E^\circ_{\text{cell}}$, of a cell made of a Co$^{2+}$/Co half-cell and a Fe$^{3+}$/Fe$^{2+}$ half-cell.
(i) Complete the table with the substance used to make the electrode in each of these half-cells.
| half-cell | electrode |
| :--- | :--- |
| Co$^{2+}$/Co | |
| Fe$^{3+}$/Fe$^2+$ | |
(ii) Write the equation for the overall cell reaction.
[1]
(iii) Use the Data Booklet to calculate the $E^\circ_{\text{cell }}$.
$$E^\circ_{\text{cell }} = \text{V}$$
(e) The electrochemical cell in (d) was set up again but this time the concentration of Co$^{2+}(\text{aq})$ was 0.050 mol dm$^{-3}$.
The Nernst equation can be used to calculate the value of an electrode potential at different concentrations.
$$E = E^5 Compound F contains the elements carbon, hydrogen and oxygen only. All carbon-carbon bonds in F are single bonds. The structure of F was analysed by mass spectrometry and infra-red and NMR spectroscopy.
(a) The mass spectrum shows that the $m/e$ value for the M peak is 90.
The ratio of the heights of the M and M+1 peaks is 22.1:0.7.
(i) Use the ratio of the heights of the M and М+1 peaks to calculate the number of carbon atoms in a molecule of F.
number of carbon atoms = ..... [2]
(ii) Suggest the molecular formula of F.
$$\text{molecular formula} = \text{CHO}$$
(b) The infra-red spectrum of F was obtained.
Use the Data Booklet and your knowledge of infra-red spectroscopy to identify the type of bond and the functional group responsible for these three absorptions.
| absorption/(c) F was dissolved in deuterated trichloromethane, CDC$l_3$, and the proton NMR spectrum of this solution obtained. (i) Use the Data Booklet and your answer to (a)(ii) to complete Table 1 for the proton NMR spectrum of F. The actual chemical shifts for the four absorptions in F have been added for you. Table 1 | $\delta$/ppm | type of proton | relative peak area | | :--- | :---: | :---: | | 1.4 | | | | 3.9 | | | | 4.7 | | | | 12.9 | | | (ii) Describe and explain the splitting pattern for the absorption at $\delta = 1.4$. [1] (iii) F was dissolved in D$_2$O and the proton NMR spectrum of this new solution obtained. Two of the absorptions in Table 1 were not present in this spectrum. Which absorptions were **not** present? and [1] (iv) Suggest the structure of F.
(d) Molecules of cycloheptadiene, $C_7H_{10}$, consist of a seven-membered ring with two carbon-carbon double bonds.
(i) Complete the skeletal formulae of two isomers of cycloheptadiene.
The isomers P and Q were analysed using carbon-13 NMR spectroscopy.
(ii) Predict the number of peaks that will be seen in the carbon-13 NMR spectra of P and Q.
| isomer | number of peaks |
| :--- | :--- |
| P | |
| Q | |
[Total: 15]Question 6 starts on the next page.
6 Ibuprofen and paracetamol are pain-relief drugs. (a) Ibuprofen and paracetamOL both contain the aryl (benzene) functional group. Name the other functional groups present in each molecule. ibuprofen ... paracetamol ... [2] (b) Ibuprofen contains a chiral centre and shows stereoisomerism. (i) State what is meant by the term chiral centre. [1] (ii) Draw the two stereoisomers of ibuprofen.
(c) Draw the structures of the organic products when ibuprofen and paracetamol react separately with LiAlH₄. (d) A student carried out some reactions with solutions of ibuprofen and paracetamOL using reagents D and E and the following results were obtained. (√ means a reaction took place.) | reagent | ibuprofen | paracetamol | | :---: | :---: | :---: | | D | √ | X | | E | X | √ | (i) Suggest a possible identity for each reagent D and E. D .... E .... (ii) Give the structure of the organic product formed when reagent D reacted with ibuprofen. (iii) Give the structure of the organic product formedwhen reagent E reacted with paracetamol.
(e) One of the steps in the manufacture of ibuprofen is shown. (i) Write an equation for the reaction between CH$_3$COCl and AlCl$_3$. [1] (ii) Complete the mechanism for the conversion of X into Y. Include all necessary curly arrows, any relevant dipoles and charges. [3] (iii) Name the mechanism in (ii). [1] [Total: 16]
Question 7 starts on the next page.
7 (a) Sodium chlorate(I), NaClO, is the active ingredient in commercial bleach. The concentration of chlorate(I) ions was determined by titration.
- $10.0\text{ cm}^3$ of a bleach solution was diluted to $250\text{ cm}^3$ in a volumetric flask using distilled water.
- Dilute sulfuric acid and an excess of potassium iodide solution were added to a $25.0\text{ cm}^3$ portion of this solution to liberate iodine.
- The resulting solution required $20.80\text{ cm}^3$ of $0.100\text{ mol dm}^{-3}$ aqueous sodium thiosulfate solution to react with the iodine produced.
The titration reactions are shown.
$$\text{C l O}^- + 2 \text{ I}^- + 2 \text{ H}^+ \rightarrow \text{I}_2 + \text{ C l}^- + \text{H}_2\text{O}$$
$$\text{I}_2 + 2 \text{S}_2\text{O}_3^{2-} \rightarrow 2 \text{I}^- + \text{S}_4\t(c) The concentration of chlorate(I) ions can also be determined by adding an excess of hydrogen peroxide to the sample of bleach and measuring the volume of oxygen gas produced.
$$\text{H}_2\text{O}_2 + \text{NaClO} \rightarrow \text{NaCl} + \text{O}_2 + \text{H}_2\text{O}$$
When an excess of aqueous hydrogen peroxide was added to $5.0\text{cm}^3$ of a different bleach solution, $82\text{cm}^3$ of oxygen was produced at room temperature and pressure.
Calculate the concentration of $\text{ClO}^{-}$ ions in this bleach solution.
concentration of $\text{ClO}^{-} = \dots\dots\dots\dots\ldots\ldots\ldots\ldotting\ldots\ldots\ldots\text{mol dm}^{-3}$ [2]
(d) Trichlorocyanuric acid, $\text{C}_3\text{Cl}_3\text{N}_3\text{O}_3$, acts as a chlorine buffer and disinfectant for swimming pools. I(iii) The decomposition of HClO is a redox reaction.
Suggest an equation for this reaction.
[1]
(e) The buffer solution in blood is a mixture of carbonic acid, $H_2CO_3$, and hydrogencarbonate ions, $HCO_3^-$. Healthy blood has a pH of 7.40.
$$H_2CO_3 + H_2O \rightleftharpoons HCO_3^- + H_3O^+ \quad K_a = 7.94 \times 10^{-7} \text{ mol dm}^{-3}$$
(i) Explain how this buffer system acts to control the blood pH. Include equations in your answer.
[2]
(ii) A patient’s blood has a $[HCO_3^-] : [H_2CO_3]$ ratio of 9.5:1.
Calculate the pH of the patient’s blood.
$$pH = \dots\dots\dots\dots\quad [2]$$
[Total: 16]
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