Cambridge International AS & A Level
* 8 9 3 6 5 2 3 2 3 2 *
CHEMISTRY 9701/42
Paper 4 A Level Structured Questions May/June 2023
2 hours
You must answer on the question paper.
No additional materials are needed.
INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.
INFORMATION
● The total mark for this paper is 100.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.
● Important values, constants and standards are printed in the question paper.
..................................................................................................................................... [2]
o
(ii) The lattice energy of the Group 2 carbonates, ΔH latt (MCO3), becomes less exothermic
down the group.
o
The lattice energy of the Group 2 oxides, ΔH latt (MO), also becomes less exothermic
down the group.
o o
ΔH latt (MCO3) and ΔH latt (MO) change by different amounts going down the group.
Suggest how the standard enthalpy change of the decomposition reaction for Group 2
carbonates changes down the group.
Explain your reasoning in terms of the relative sizes of the anions and the relative
changes in lattice energy down the group.
(c) Potassium sulfite, K2SO3, is used as a food additive.
The concentration of sulfite ions, SO32–, can be determined by titration using aqueous
acidified manganate(VII) ions, MnO4–.
• A 250 cm3 solution contains 3.40 g of impure K2SO3.
• 25.0 cm3 of this solution requires 22.40 cm3 of 0.0250 mol dm–3 acidified MnO4– to
reach the end-point. All the SO32– ions are oxidised. None of the other species in
the impure K2SO3 are oxidised.
The reaction occurs as shown by the two half-equations.
H2O + SO32– SO42– + 2H+ + 2e–
MnO4– + 8H+ + 5e– Mn2+ + 4H2O
(i) Give the ionic equation for the reaction between SO32– and acidified MnO4–.
(ii) Samples of [Co(H2O)6]2+ are reacted separately with an excess of aqueous ammonia,
with an excess of concentrated HCl and with an excess of aqueous sodium hydroxide,
as shown in Fig. 2.1.
excess excess
NH3(aq) NaOH(aq)
A [Co(H2O)6]2+(aq) C
excess
concentrated HCl
B
Fig. 2.1
Complete Table 2.1 about the reactions shown by [Co(H2O)6]2+.
Table 2.1
reagent added to formula of cobalt colour and state of
type of reaction
[Co(H2O)6]2+(aq) species formed cobalt species formed
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