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3 marksBuffers and pH

CAPE Chemistry Unit 1 · May/June 2024 · Paper 2 · Question 2(e)(ii)

A buffer solution containing 0.2 mol dm^-3 of a weak acid, HA, and 0.5 mol dm^-3 of the sodium salt of the weak acid, NaA, was prepared for use in the food industry.

Given that Ka for the weak acid = 7.4 * 10^-4 mol dm^-3, calculate the pH of the buffer solution.

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Other parts of this question

  1. 2(a)What is meant by the term 'dynamic equilibrium'?[2 marks]
  2. 2(b)(i)Write an expression for the equilibrium constant of the reverse reaction.[1 mark]
  3. 2(b)(ii)State the numerical value of the equilibrium constant for the reverse reaction based on the expression in (b)(i).[1 mark]
  4. 2(c)State Le Chatelier's principle.[2 marks]
  5. 2(d)(i)Use Le Chatelier's principle to predict and explain the effect of increasing the pressure on Equilibrium A.[2 marks]
  6. 2(d)(ii)Use Le Chatelier's principle to predict and explain the effect of decreasing the temperature on Equilibrium A.[2 marks]
  7. 2(d)(iii)Use Le Chatelier's principle to predict and explain the effect of increasing [H^+(aq)] on Equilibrium B.[2 marks]
  8. 2(e)(i)Define the term 'buffer solution'.[2 marks]
  9. 2(f)Outline the experimental procedure which can be used to prepare a sample of the buffer solution in (e). Include tests used to confirm a buffer solution was…[5 marks]
  10. 2(g)With the aid of equations, explain how a solution of ammonium sulfate and ammonia can control pH.[4 marks]
  11. 2(h)Define the term 'half-life'.[2 marks]
  12. 2(i)Using a Boltzmann distribution curve, show how a catalyst affects the rate of a chemical reaction.[2 marks]

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