科目：化学 Chemistry (9701)
年份：2024 冬季
试卷：Paper 42
总页数：23
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 (a) The equation for reaction 1 is shown.
reaction 1 $X \rightarrow 2Y$
Reaction 1 is first order with respect to the concentration of X. The half-life of the reaction, $t_{\frac{1}{2}}$, is 900 s at 20 °C.
(i) A solution of X with a concentration of 0.180 mol dm$^{-3}$ is prepared at 20 °C. Calculate the average rate of reaction 1 over the first 1800 s.
$$\text{average rate of reaction 1} = ...$$ [2]
(ii) Complete the rate equation for reaction 1.
$$\text{rate} = ...$$ [1]
(iii) Show that the rate constant, $k$, is $7.70 \times 10^{-4}\text{s}^{-1}$ at 20 °C.
[1]
(iv) Calculate the initial rate of reaction 1 when the concentration of X is 0.150 mol dm$^{-3}$.
Include units.
$$\text{rate} = ... \text{units}$$ [2]
(b) Catalysts may be homogeneous or heterogeneous.
(i) Platinu(iii) Platinum acts as a heterogeneous catalyst in the removal of nitrogen dioxide, NO₂, from the exhaust gases of car engines.
Describe the mode of action of a platinum catalyst in this process.
[2]
(iv) NO₂ acts as a homogeneous catalyst in the oxidation of atmospheric sulfur dioxide, SO₂. Write equations for the two reactions that occur.
equation 1 ... [1]
equation 2 ... [1]
(c) SO₂ dissolves in water, forming H₂SO₃.
H₂SO₃ can be oxidised under acidic conditions.
The relevant electrode reaction and its E° value are shown.
$$\text{SO}_4^{2-} + 4\text{H}^+ + 2\text{e}^- \rightleftharpoons \text{H}_2\text{SO}_3 + \text{H}_2\text{O}$$
E° = +0.17 V
Four more half-equations for reactions occurring under acidic conditions, and their E° values, are shown.
$$\text{H}_3\text{BO}_3 + 3\2 (a) Predict and explain the variation in enthalpy change of hydration for the ions Na$^{+}$, Mg$^{2+}$ and Al$^{3+}$.
[3]
(b) Fig. 2.1 shows an incomplete energy cycle.
Fig. 2.1
(i) Complete line C on Fig. 2.1. Include state symbols. [1]
(ii) Use both words and symbols to identify change 2 on Fig. 2.1.
Use changes 1 and 3 as examples of how this should be done. [2](iii) Calculate a value for the lattice energy of magnesium chloride, $\Delta H_{\text{latt}} \text{ MgCl}_2(\text{s})$, by selecting and using appropriate data from Table 2.1.
Table 2.1
| energy change | value/kJ mol$^{-1}$ |
| :--- | :--- |
| enthalpy change of solution of magnesium chloride | $-155$ |
| enthalpy change of formation of magnesium chloride | $-642$ |
| first ionisation energy of magnesium | $+736$ |
| second ionisation energy of magnesium | $+1450$ |
| electron affinity of chlorine | $-349$ |
| enthalpy change of hydration of Mg$^{2+}$ | $-1920$ |
| enthalpy change of hydation of Cl$^-$ | $-364$ |
$\Delta H_{\text{latt}} \mathrm{MgCl}_2(\text{s}) = \dots\dots\dots\dots\mathrm{kJ mol}^{-1}$ [3]
(c) Define entropy.
[1]
(d) At $25^{\circ}\mathrm{C}$ the enthalpy change (e) (i) Use your answer to (d) to predict whether or not Z is soluble in water at 25°C. Explain your answer. [1] (ii) Predict whether Z becomes more or less soluble as the water is heated from 25°C to 95°C. Explain your answer. [Total: 14]
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3 (a) The pH of a saturated solution of calcium hydroxide is 12.35 at 298 K.
(i) Show that the concentration of hydroxide ions in a saturated solution of calcium hydroxide is $0.0224 \text{ mol dm}^{-3}$ at 298 K.
[2]
(ii) Use data given in (i) to calculate the solubility product, $K_{\text{sp}}$, of calcium hydroxide at 298 K.
Include the units of $K_{\text{sp}}$ in your answer.
$$K_{\text{sp}} = \dots\dots\dots\dots\quad\text{units}\quad\dots\dots\dots$$
(iii) A spatula measure of solid calcium chloride is stirred into a sample of saturated calcium hydroxide solution. All of the calcium chloride dissolves.
Describe one other observation that would be made and give an estimated value of the pH of the solution obtained.
Explain both your answers.
observation ...
pH of solution ...(b) Some solid calcium is added to an excess of aqueous ethanoic acid, CH$_3$COOH, and left until all the calcium has reacted. The resulting mixture, mixture D, contains no undissolved solids.
(i) Write an equation for the reaction of calcium with CH$_3$COOH.
(ii) Use formulae of molecules and ions to identify two conjugate acid–base pairs present in mixture D.
Pair 1 should consist of organic species.
pair 1: ..... conjugate acid conjugate base
pair 2: ..... conjugate acid conjugATE base
(iii) Write the expression for the $K_a$ of CH$_3$COOH.
$$K_a =$$
[1]
(iv) The concentration of calcium ethanoate, (CH$_3$COO)$_2$Ca, in mixture D is 0.394 mol dm$^{-3}$. The concentration of CH$_3$COOH in mixture D is 0.270 mol dm$^{-3}$.
The $K_a$ of CH$_3$ COOH is $1.74 \times 10^{-5}$ mol dm4 Transition metal atoms and transition metal ions form complexes by combining with species called ligands.
(a) When NaOH(aq) is added to an aqueous solution containing $[\text{Co}(\text{H}_2\text{O})_6]^{2+}$ a precipitation reaction occurs accompanied by a colour change.
In this reaction two of the water ligands each lose one H$^+$ ion. The H$^+$ ions are gained by OH$^{-}$ ions from the NaOH(aq).
(i) State the colour change seen in this precipitation reaction.
from ... to ... [1]
(ii) Complete the ionic equation for this precipitation reaction.
$$[\text{Co}(\text{H}_�\text{O})_6]^{2}+ \rightarrow +$$ [1]
(iii) This precipitation reaction can also be described as a different type of reaction.
Name this type of reaction.
... [1]
(b) L is an uncharged tridentate ligand. L donates thr(c) The mineral chromite contains a compound which has the formula FeCr$_n$O$_4$. The oxidation state of iron in FeCr$_n$O$_4$ is +2.
A sample of 4.18 g of FeCr$_n$O$_4$is dissolved in an excess of sulfuric acid. The resulting solution is made up to 250 cm$^3$. This is solution F.
All the Fe$^{2+}$ ions in 25.0 cm$^3$ of solution F are oxidised to Fe$^{3+}$ ions by exactly 18.7 cm$^3$ of 0.0200 mol dm$^{-3}$ KMnO$_4$.
One MnO$_4^-$ ion reacts with five Fe$^{2+}$ ions. Assume no other oxidation reaction occurs.
(i) Write an equation for the reaction of Fe$^{2+}$ ions with MnO$_4^-$ ions in acid solution.
[1]
(ii) Calculate the number of moles of Fe$^{2+}$ ions in $25.0\text{cm}^3$ of solution F.
number of moles of Fe$^{2+}$$\text{ions} = \dots\dots\dots\dots\ldots\ldots\ldots\ldotp$ 5 Ni$^{2+}$ ions form a number of different complex ions, including $[\text{Ni}(\text{H}_2\text{O})_6]^{2+}$, $[\text{Ni}(\text{NH}_3)_6]^{2+}$ and $[\text{Ni}(en)_3]^{2+}$.
The abbreviation en represents 1,2-diaminoethane. The numerical values of two stability constants, $K_{\text{stab}}$, are given in Table 5.1.
Table 5.1
| complex | $K_{\text{stab}}$ |
| :--- | :--- |
| $[\text{Ni}(\text{NH}_{3})_{6}]^{2+}$ | $4.8 \times 10^7$ |
| $[\text{Ni}(en)_{3}]^{2+}$ | $2.0 \times 10^{18}$ |
(a) Complete the expression for the $K_{\text{stab}}$ of $[\text{Ni}(en)_3]$$^{2+}$.
$$K_{\text{stab}} =$$
[1]
(b) A solution of $[\text{Ni}(\text{H}_{2}\text{O})_{6}]^{2+}$ is added to a solution that contains $0.10\,\text{mol}\,\text{dm}^{-3}\,\text{NH}_{3}$ and $0.10\,\text{ mol}\,\text{dm}^{-3}en$.(c) Complete Fig. 5.1 to show the three-dimensional structures of the two isomers of $[\text{Ni}(en)_3]^{2+}$.
Use N to represent the en ligand.
Name the type of isomerism shown.
Fig. 5.1
type of isomerism shown ..... [3]
[Total: 6]6 Fig. 6.1 shows two reactions of ethanedioic acid, HOOCCOOH.
(a) (i) Draw the organic product G in the box in Fig. 6.1.
[1]
(ii) In Fig. 6.1, SOC$l_2$ is given as the reagent that reacts with HOOCCOOH to produce G. Identify a different reagent that also reacts with HOOCCOOH to produceG.
[1]
(b) Identify two different reagents that oxidise HOOCCOOH to form carbon dioxide and water.
[2]
(c) HOOCCOOH ionises as shown.
$$\text{HOOCCOOH} \rightleftharpoons \text{HOOCCOO}^- + \text{H}^+$$
HOOCCOOH is a much stronger acid than methanoic acid, HCOOH. Suggest an explanation for this difference in acidity.
[2](d) Benzene-1,4-dicarboxylic acid, HOOC$_6$H$_4$COOH, can be made from benzene, C$_6$H$_6$, in two steps as shown in Fig. 6.2.  (i) Suggest the identity of J by drawing its structure in the box in Fig. 6.2. [1] (ii) Identify the reagents and conditions for step 1 and step 2. step 1 ..... [2] step 2 ..... [2] (iii) Draw the structure of exactly one repeat unit of the polymer formed when benzene-1,4-dicarboxyolic acid reacts with ethane-1,2-diol, HOCH$_2$CH$_2$OH. The linkage formed between the monomers should be shown fully displayed. [2] (iv) State the type of polymerisation that occurs when benzene-1,4-diarboxylic acid reacts with ethane-1,Z-diol and name the linkage formed between the monomers. type of polymerisation ..... [1] linkage ..... [1] [Total: 12]
7 Benzene reacts with chlorine gas to form chlorobenzene. This reaction can be described as the reaction between benzene molecules and $Cl^+$ ions. The $Cl^+$ ions are formed by adding a suitable catalyst to the chlorine gas. (a) Give the name or formula of a catalyst that can be used for this reaction. (b) The mechanism for this reaction is shown. (i) The movement of a pair of electrons is represented by $x$ in diagram 1. • State where this pair of electrons is **before** step 1 takes place. • State where this pair of electrons is **[after]** step 1 has taken place. [2] (ii) The movement of another pair of electrons is represented by $y$ in diagram 2. • State where this pair of electrons是 **before** step 2 takes place. • State where this pair of electron是 **[after]** step 2 has tak
(d) Complete the equation for this reaction between benzene and chlorine.
$$C_6H_6 + \text{...} \rightarrow \text{...} + \text{...}$$
[1]
(e) The mechanism for this reaction is electrophilic substitution.
Complete the following sentence. Write formulae in the gaps provided.
During this reaction, the electrophile is ... and a ... atom in benzene is substituted by a ... atom.
[1]
(f) Chloroethane reacts with NaOH(aq). Chlorobenzene does not.
(i) Name the mechanism of the reaction that chloroethane undergoes with NaOH(aq), and identify the major organic product that is formed.
mechanism ...
major organic product ...
[1]
(ii) Explain the difference in reactivity of chloroethane and chlorobenzene when treated with NaOH(aq).
[2]
Total: 118 The amino acid serine, HOCH$_2$CH(NH$_2$)COOH, exists in two optically active forms. These optical isomers, isomer P and isomer Q, are shown in Fig. 8.1. Fig. 8.1 (a) Isomer P and isomer Q have identical physical and chemical properties, with the exception of two specific properties. One of these two properties is their differing effect on plane polarised light. State the other property by which they differ. [1] (b) A solution of pure isomer P of a particular concentration rotates plane polarised light by $5.0^\circ$ in a clockwise direction. Describe how a solution of pure isomer Q of the same concentration affects plane polarised light. [1] (c) State another term, in addition to stereoisomers, optical isomers and non-superimposable mirror images, which can be used to describe t
(f) Complete Table 8.1 to describe the peaks seen in the proton ($^1\text{H}$) NMR spectrum of HOCH$_2$CH(NH$_2$)COOH dissolved in D$_2$O.
Use as many rows in Table 8.1 as you need to, leaving the other rows blank.
Table 8.1
| group responsible for peak | name of splitting pattern shown by peak | explanation for splitting pattern |
| :--- | :---: | :---: |
| | | |
| | | |
(g) Proline is a naturally occurring amino acid. The skeletal formula of proline is shown.
$$\text{proline}$$
State the number of peaks in the carbon-13 ($^{13}\text{C}$) NMR spectrum of proline.
[1](h) Glutamic acid is a naturally occurring amino acid.
The skeletal formula of glutamic acid is shown.
$$\text{glutamic acid}$$
The isoelectric point of glutamic acid is pH3.
A sample of glutamic acid is dissolved in a solution of pH1. A strong alkali is then added until the pH of the mixture reaches pH14. During this process all possible ionised forms of glutamic acid are present at different times, depending on the pH of the solution.
Complete the boxes below to show four different ionised forms of glutamic acid that are present at the stated pH values.
at pH1 at pH3 at pH9 at pH14
[Total: 12]21 BLANK PAGE
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Important values, constants and standards
| | |
| :--- | :--- |
| molar gas constant $R = 8.31 \text{ JK}^{-1}\text{mol}^{-1}$ | |
| Faraday constant $F = 9.65 \times 10^4\text{ C mol}^{-1}$ | |
| Avogadro constant $L = 6.022 \times 10^{23}\text{ mol}^{-1}$ | |
| electronic charge $e = -1.60 \times 10^{-19}\text{ C}$ | |
| molar volume of gas $V_m = 22.4 \text{ dm}^3\text{ mol}^{-1}$ at s.t.p. (101 kPa and 273 K) $V_m = 24.0 \text{ dm}^3\text{mol}^{-1}$ at room conditions | |
| ionic product of water $K_w = 1.00 \times 10^{-14} \text{ mol}^2\text{dm}^{-6}$ (at 298 K (25 °C)) | |
| specific heat capacity of water $c = 4.18 \text{ kJkg}^{-1}\text{K}^{-1}$ (4.18 Jg$^{-1}$K$^{-1}$) | |The Periodic Table of Elements Group 1 2 3 Li lithium 6.9 4 Be beryllium 9.0 11 Na sodium 23.0 12 Mg magnesium 24.3 Key atomic number atomic symbol name relative atomic mass 1 H hydrogen 1.0 3 4 5 6 7 8 9 10 11 12 21 Sc scandium 45.0 22 Ti titanium 47.9 23 V vanadium 50.9 24 Cr chromium 52.0 25 Mn manganese 54.9 26 Fe iron 55.8 27 Co cobalt 58.9 28 Ni nickel 58.7 29 Cu copper 63.5 30 Zn zinc 65.4 31 Ga gallium 69.7 32 Ge germanium 72.6 33 As arsenic 74.9 34 Se selenium 79.0 35 Br bromine 79.9 36 Kr krypton 83.8 37 Rb rubidium 85.5 38 Sr strontium 87.6 39 Y yttrium 88.9 40 Zr zirconium 91.2 41 Nb nibridium 92.9 42 Mo molybdenum 95.9 43 Tc technetium - 44 Ru ruthenium 101.1 45 Rh rhodium 102.9 46 Pd palladium 106.4 47 Ag silver 107.9 48 Cd cadmium 112.4 49 In indium 114.8 50 Sn tin 118.7