AqA EXAMPRO
A-LEVEL CHEMISTRY Name:
Practice Paper 1 Maximum marks: 105 Time allowed: 2 hours
These questions are from past papers covering topics and skills based on the advance
information to help you prepare for the exams this summer.
Answer all questions in the spaces provided.
You will need the Periodic Table/Data Booklet
1 In this question, give all values of pH to 2 decimal places.
(a) The ionic product of water has the symbol Kw
(i) Write an expression for the ionic product of water.
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(1)
(ii) At 42°C, the value of Kw is 3.46 × 10−14 mol2 dm−6.
Calculate the pH of pure water at this temperature (to 2 decimal places).
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(2)
(iii) At 75 °C, a 0.0470 mol dm–3 solution of sodium hydroxide has a pH of
11.36.
Calculate a value for Kw at this temperature.
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(2)
Page 1
,(b) Methanoic acid (HCOOH) slightly dissociates in aqueous solution.
(i) Write an equation for this dissociation.
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(1)
(ii) Write an expression for the acid dissociation constant Ka for methanoic
acid.
__________________________________________________________
__________________________________________________________
(1)
(iii) The value of Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25 °C.
Calculate the pH of a 0.0560 mol dm−3 solution of methanoic acid.
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(3)
(iv) The dissociation of methanoic acid in aqueous solution is endothermic.
Deduce whether the pH of a solution of methanoic acid will increase,
decrease or stay the same if the solution is heated. Explain your answer.
Effect on pH _______________________________________________
Explanation ________________________________________________
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(3)
Page 2
, (c) The value of Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25°C.
A buffer solution is prepared containing 2.35 × 10−2 mol of methanoic acid and
1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C (to 2 decimal places).
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(3)
(ii) A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the
buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
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(4)
20
Page 3
A-LEVEL CHEMISTRY Name:
Practice Paper 1 Maximum marks: 105 Time allowed: 2 hours
These questions are from past papers covering topics and skills based on the advance
information to help you prepare for the exams this summer.
Answer all questions in the spaces provided.
You will need the Periodic Table/Data Booklet
1 In this question, give all values of pH to 2 decimal places.
(a) The ionic product of water has the symbol Kw
(i) Write an expression for the ionic product of water.
__________________________________________________________
(1)
(ii) At 42°C, the value of Kw is 3.46 × 10−14 mol2 dm−6.
Calculate the pH of pure water at this temperature (to 2 decimal places).
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(2)
(iii) At 75 °C, a 0.0470 mol dm–3 solution of sodium hydroxide has a pH of
11.36.
Calculate a value for Kw at this temperature.
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(2)
Page 1
,(b) Methanoic acid (HCOOH) slightly dissociates in aqueous solution.
(i) Write an equation for this dissociation.
__________________________________________________________
(1)
(ii) Write an expression for the acid dissociation constant Ka for methanoic
acid.
__________________________________________________________
__________________________________________________________
(1)
(iii) The value of Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25 °C.
Calculate the pH of a 0.0560 mol dm−3 solution of methanoic acid.
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(3)
(iv) The dissociation of methanoic acid in aqueous solution is endothermic.
Deduce whether the pH of a solution of methanoic acid will increase,
decrease or stay the same if the solution is heated. Explain your answer.
Effect on pH _______________________________________________
Explanation ________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(3)
Page 2
, (c) The value of Ka for methanoic acid is 1.78 × 10−4 mol dm−3 at 25°C.
A buffer solution is prepared containing 2.35 × 10−2 mol of methanoic acid and
1.84 × 10−2 mol of sodium methanoate in 1.00 dm3 of solution.
(i) Calculate the pH of this buffer solution at 25°C (to 2 decimal places).
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(3)
(ii) A 5.00 cm3 sample of 0.100 mol dm−3 hydrochloric acid is added to the
buffer solution in part (c)(i).
Calculate the pH of the buffer solution after this addition.
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
(4)
20
Page 3
