Quelpr
5 marksTitrimetric (Volumetric) Methods of Analysis

CAPE Chemistry Unit 2 · 2006 · Paper 2 · Question 5(d)(ii)

A buffer solution is made by adding 6.56 g of sodium ethanoate, CH₃COONa, to 1 dm³ of 0.02 M ethanoic acid, CH₃COOH.

K_a for ethanoic acid is equal to 1.8 × 10⁻⁵ mol dm⁻³. Write the expression for K_a and use it to calculate the pH of the buffer solution. State any assumptions made in the calculation.

The mark scheme is shown once you've answered.

Practise this question

Other parts of this question

  1. 5(a)Define the term 'buffer solution'.[2 marks]
  2. 5(b)(i)Suggest a reason for adding a buffer to the pool.[1 mark]
  3. 5(b)(ii)Use the equation HCO₃⁻(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CO₃²⁻(aq) to explain how the aqueous hydrogen carbonate ion acts as a buffer.[2 marks]
  4. 5(c)(i)Explain how the molecular structure of amino acids relates to their function as buffers in human blood.[3 marks]
  5. 5(c)(ii)State ONE industry in which buffers are used.[1 mark]
  6. 5(d)(i)Calculate the concentration of the sodium ethanoate solution in mol dm⁻³.[2 marks]
  7. 5(e)(i)Find the new concentrations of sodium ethanoate and ethanoic acid.[2 marks]
  8. 5(e)(ii)Comment on the pH of the new solution and explain your answer.[2 marks]

More practice: the rest of this paper · more Titrimetric (Volumetric) Methods of Analysis questions · all CAPE Chemistry Unit 2 past papers