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5 marksBuffers and pH

CAPE Chemistry Unit 1 · 2013 · Paper 2 · Question 2(c)

Calculate the pH of a buffer solution made from 20.00 cm³ of 0.10 mol dm⁻³ propanoic acid (CH₃CH₂COOH) and 40.00 cm³ of 0.050 mol dm⁻³ sodium propanoate (CH₃CH₂COONa). (The acid dissociation constant, Kₐ, for propanoic acid is 1.22 × 10⁻⁵.)

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Other parts of this question

  1. 2(a)Define the term 'buffer solution'.[2 marks]
  2. 2(b)(i)Explain, using relevant equations, how a buffer solution containing ammonia and ammonium chloride reacts when contaminated with a small quantity of base.[2 marks]
  3. 2(b)(ii)Explain, using relevant equations, how a buffer solution containing ammonia and ammonium chloride reacts when contaminated with a small quantity of acid.[2 marks]
  4. 2(d)(i)List TWO relevant pieces of apparatus and/or materials that may have been used to carry out the experiment.[2 marks]
  5. 2(d)(ii)Describe TWO relevant steps taken by the students to determine the pH of the buffer.[2 marks]

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