Oxford Cambridge and RSA
*1349593883*
Friday 21 June 2025 – Morning
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2024 [601/5255/2] DC (PQ/SW) 331429/6
OCR is an exempt Charity
, 2
Turn over
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 = ...................
(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 = ...................
(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] (d) A student is provided with hydrated copper(II) nitrate,
Cu(NO3)2•3H2O.
© OCR 2024
, 3
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
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........................................................................................................................................
............ [5]
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?
...............................................................................................................................................
...........
...............................................................................................................................................
...... [1]
(ii) Determine the C–H bond enthalpy, in kJ mol–1, using the information above.
C–H bond enthalpy = ........................................... kJ mol
(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.
© OCR 2024
*1349593883*
Friday 21 June 2025 – Morning
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2024 [601/5255/2] DC (PQ/SW) 331429/6
OCR is an exempt Charity
, 2
Turn over
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 = ...................
(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 = ...................
(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] (d) A student is provided with hydrated copper(II) nitrate,
Cu(NO3)2•3H2O.
© OCR 2024
, 3
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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..................
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..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
© OCR 2024 Turn over
, 4
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............ [5]
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?
...............................................................................................................................................
...........
...............................................................................................................................................
...... [1]
(ii) Determine the C–H bond enthalpy, in kJ mol–1, using the information above.
C–H bond enthalpy = ........................................... kJ mol
(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.
© OCR 2024
