Exam (elaborations)
OCR MERGED QUESTION PAPER AND MARK SCHEME A Level Chemistry AH432/03Unified chemistry FOR JUNE 2024
OCR MERGED QUESTION PAPER AND MARK SCHEME A Level Chemistry AH432/03Unified chemistry FOR JUNE 2024
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Friday 21 June 2024 – MorningA Level Chemistry A
H432/03 Unified chemistry
Time allowed: 1 hour 30 minutes
Turn over
, 2
1 This question is about acids, bases and salts.
(a) What is the pH of 1.00 dm3 of 0.400 mol dm–3 of NaOH(aq) at 298 K?
pH = ................... [2]
(b) Water is added to 10.0 cm3 of 0.750 mol dm–3 HCl (aq) to produce 100 cm3 of diluted HCl (aq).
What is the pH of the diluted HCl (aq)?
Give your answer to 2 decimal places.
pH = ................... [1]
(c) A solution has concentrations of 0.300 mol dm–3 CH3COOH(aq) and 0.100 mol dm–3
CH3COONa(aq).
Ka for CH3COOH = 1.75 × 10–5 mol dm–3 at 298 K.
What is the pH of the solution at 298 K?
Give your answer to 2 decimal places.
pH = ................... [2]
© OCR 2024
, 3
(d) A student is provided with hydrated copper(II) nitrate, Cu(NO3)2•3H2O.
The student needs to prepare a standard solution of Cu(NO3)2•3H2O with a concentration of
0.200 mol dm–3. The student has access to usual laboratory apparatus and equipment.
Describe how the student would prepare 100.0 cm3 of this solution, giving quantities, apparatus
and method.
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© OCR 2024 Turn over
, 4
2 This question is about different areas of chemistry.
(a) Hydrogen gas is manufactured by the chemical industry from the reversible reaction of methane
and steam, shown below.
CH4(g) + H2O(g) 3H2(g) + CO(g) ΔH = +195 kJ mol–1
Average bond enthalpies are shown in the table.
Bond H–H O–H C≡O
Average bond enthalpy
+436 +464 +1077
/ kJ mol–1
(i) Why do all average bond enthalpies have a positive value?
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..................................................................................................................................................... [1]
(ii) Determine the C–H bond enthalpy, in kJ mol–1, using the information above.
C–H bond enthalpy = ........................................... kJ mol–1 [3]
(iii) Hydrogen gas is being considered as a household fuel to replace methane.
The enthalpy change of formation, ΔfH, for H2O(l) is –285.8 kJ mol–1.
Determine the energy released when 60.0 m3 of hydrogen is used as a household fuel at RTP.
Give your answer to 3 significant figures and in standard form.
energy released = .................................................... kJ [2]
© OCR 2024
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