9701/42/o/n/21 © Ucles 2021
9701/42/o/n/21 © Ucles 2021
9701/42/o/n/21 © Ucles 2021
(a) Define .
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Some data relating to radium and sulfur are listed. Select relevant data from this list for use in your
answers to parts (b) to (e).
(b) Write an equation for the process corresponding to the second electron affinity of sulfur.
Include state symbols.
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Use the data in this question to calculate the enthalpy change for the reaction S8(s) → 8S(g).
(e) (i) State the two major factors that affect the numerical magnitude of a lattice energy.
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(ii) For each factor you have identified in (e)(i), state whether it tends to make the lattice
energy of radium sulfide more or less exothermic than that of sodium chloride.
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(iii) The lattice energies of sodium chloride, NaCl, and radium sulfide, RaS, are –771 kJ mol–1
and –2612 kJ mol–1, respectively.
Identify the dominant factor in determining the relative numerical magnitudes of the lattice
energies of radium sulfide and sodium chloride.
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[Total: 13]
2 Ethoxyethane, C2H5OC2H5, can dissolve both in water and in octan-1-ol. The expression and
numerical value for the partition coefficient of ethoxyethane between water and octan-1-ol are
given. Water and octan-1-ol are immiscible.
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(b) A second experiment is performed and the value of Kpc is found to be 6.760. The concentration
of ethoxyethane in the octan-1-ol layer is 7.62 g dm–3.
(ii) 100 cm3 of the octan-1-ol layer is taken and shaken with 100 cm3 of water.
Calculate the maximum amount, in mol, of ethoxyethane that can be extracted into the
water.
(i) Use these data to calculate a value for the solubility product, Ksp, of lead(II) iodide.
Ksp = ..............................
units = ..............................
[2]
Describe and explain what is seen if a few drops of saturated potassium iodide solution
are added to a portion of solution X.
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[Total: 10]
3 Pure water is a very poor conductor of electricity. However, when hydrogen chloride gas is dissolved
in water, ions are formed and a current flows during electrolysis.
The overall change after electrolysis is that hydrogen chloride gas is converted into hydrogen and
chlorine.
When a current of 3.10 A is passed through the solution for Y minutes, 351 cm3 of chlorine are
produced at the anode, measured under room conditions.
(a) Calculate the number of chlorine molecules produced during the electrolysis.
(b) Calculate the total number of electrons transferred to produce this number of chlorine molecules.
(c) Calculate the quantity of charge, in coulombs, of the total number of electrons calculated in (b).
(d) Calculate the time, Y, in minutes, for which the current flows.
(ii)
∆H o for the reaction 2HCl (g) → H2(g) + Cl 2(g) is +185 kJ mol–1.
(iii) Predict the effect of increasing temperature on the spontaneity of this reaction. Explain
your answer.
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[Total: 9]
4 Separate samples of 0.01 mol of magnesium nitrate and 0.01 mol of strontium nitrate are heated
until completely decomposed to the metal oxide, nitrogen dioxide and oxygen.
(a) State which of these two Group 2 nitrates requires the higher temperature before it begins to
decompose. Explain your answer.
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(b) After decomposition is complete the 0.01 mol sample of magnesium oxide is taken and
increasing amounts of water are added to it, with stirring, until no solid remains.
This procedure is repeated with the 0.01 mol sample of strontium oxide.
Identify the sample to which most water must be added to cause all the solid to dissolve.
Explain your answer by reference to the solubilities of the products formed when water is
added to the oxides. You should refer to relevant energy terms in your answer.
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(c) The nitrogen dioxide given off by the decomposition of 0.0100 mol of strontium nitrate is
dissolved in water. The oxidising agent H2O2(aq) is then added to give 150.0 cm3 of a solution
in which nitric acid, HNO3, is the only nitrogen-containing product.
(i) Calculate the concentration, in mol dm–3, of HNO3 in the 150.0 cm3 of solution.
Calculate the minimum volume, in cm3, of NaOH(aq) needed. Give your answer to three
significant figures.
volume = .............................. cm3 [1]
[Total: 7]
5 Transition elements form complexes.
(a) Molybdenum, Mo, forms an octahedral complex consisting of one Mo atom surrounded by
carbon monoxide, CO, molecules. CO is a monodentate ligand. Iron forms an octahedral
complex consisting of one Fe3+ and a number of cyanide, CN–, ions. CN– is a monodentate
ligand.
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(ii) Complete the table by stating the formulae and charges of the complexes described.
formula charge
molybdenum complex
iron(III) complex
[2]
(iii) Draw a three-dimensional diagram to show the shape of this iron(III) complex.
Fe
[1]
(b) An excess of aqueous ammonia is added to dilute copper(II) sulfate solution. A dark blue
complex, [Cu(NH3)4(H2O)2]2+, is formed.
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(ii) Explain the origin of colour in copper(II) complexes.
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(c) An excess of concentrated hydrochloric acid is added to the dark blue solution of
[Cu(NH3)4(H2O)2]2+. A new complex, Z, is formed. The colour of the solution changes.
(i) Write an equation for the formation of Z from the solution of [Cu(NH3)4(H2O)2]2+. Include the
formula and charge of Z.
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(v) Explain why the colour of a solution of [Cu(NH3)4(H2O)2]2+ is different from the colour of a
solution of Z. You should refer to the energies of the orbitals involved in your answer.
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[Total: 15]
6 An excess of aqueous ammonia is added to a solution containing the complex ion [Co(H2O)6]2+.
(a) Complete the sentence to describe the colour change that will be seen during this reaction.
Kstab =
[1]
What deduction about the properties of [Co(NH3)6]2+ and [Co(H2O)6]2+ can be made from this
Kstab value?
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(d) Oxygen can oxidise [Co(NH3)6]2+ to [Co(NH3)6]3+ under standard conditions in alkaline solutions.
(i) Use this information and the Data Booklet to calculate the value for this oxidation of
[Co(NH3)6]2+.
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= .............................. V
[1]
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(iii) Predict, by selecting suitable data from the Data Booklet, whether oxygen can oxidise
Co2+(aq) in acidic solution, in the absence of ammonia. Explain your answer.
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[Total: 7]
7 The structure of benzene-1,3-dicarboxylic acid is shown.
benzene-1,3-dicarboxylic acid
O
HO
OH
O
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State the number of peaks in the carbon-13 (13C) NMR spectrum of each compound.
benzene-1,3-dicarboxylic acid
benzene-1,4-dicarboxylic acid
[2]
(c) Benzene-1,3-dicarboxylic acid can be made by the two-step synthesis shown below.
benzene-1,3-dicarboxylic acid
compound P compound Q O
O
step 1 step 2
C9H8O3 HO
HO OH
O
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(ii) Explain why the major product of this two-step synthesis is benzene-1,3-dicarboxylic acid
and not benzene-1,4-dicarboxylic acid.
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(iii) The reagents used for step 1 are CH3COCl and Al Cl 3. These reagents give rise to
+
CH3C=O ions which react with compound P.
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+
Draw the mechanism of the reaction of CH3C=O ions with compound P. Include all
(iv)
relevant curly arrows and charges, the structure of the intermediate and the structure of
compound Q.
intermediate compound Q
+
CH3C=O
HO
[3]
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[Total: 10]
8 Alanine, H2NCH(CH3)CO2H, and glutamic acid, H2NCH(CH2CH2CO2H)CO2H, are two naturally
occurring amino acids.
[2]
(b) The proton (1H) NMR spectrum of either alanine in D2O or glutamic acid in D2O is shown.
9 8 7 6 5 4 3 2 1 0
/ ppm
State whether this is the spectrum of alanine in D2O or the spectrum of glutamic acid in D2O.
Explain your answer by reference to the number of peaks and splitting patterns.
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(c) The mass spectrum of glutamic acid, H2NCH(CH2CH2CO2H)CO2H, is obtained.
(i) State the m/e value of the molecular ion peak in this spectrum.
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(ii) The spectrum has peaks with m/e values of 88 and 131.
88
131
[2]
(d) At pH 11 alanine exists as H2NCH(CH3)CO2– ions and glutamic acid exists as
H2NCH(CH2CH2CO2–)CO2– ions. A mixture of alanine and glutamic acid at pH 11 is subjected
to electrophoresis.
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(ii) Draw a fully labelled diagram for the apparatus that would be used to carry out this
electrophoresis. Your diagram should include the position of the mixture of alanine and
glutamic acid at the start of the electrophoresis experiment. [2]
(iii) Identify the electrode that each amino acid travels towards during electrophoresis at pH 11.
alanine ................................................................................................................................
(iv) In a particular electrophoresis experiment at pH 11, the glutamic acid travels 3.4 cm.
Alanine travels a shorter distance.
Explain the factors that account for the difference in the distances travelled.
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[Total: 14]
9 Butylamine, CH3CH2CH2CH2NH2, can be synthesised from different organic compounds by using
suitable reagents. Each reaction involves one step.
[6]
(b) Compare and explain the relative basicities of ammonia, butylamine and phenylamine.
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[Total: 10]
10 (a) Complete the table to show the structure of the organic product from each reaction of phenol,
C6H5OH.
1 phenol + NaOH(aq)
2 phenol + Na(s)
+
N
N
3 phenol + (aq)
+ NaOH, at 4 °C
an excess of phenol +
O O
4
C C
Cl Cl
[4]
(b) Identify two reactions from the table in which ethanol would behave in a similar way to phenol.
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[Total: 5]