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2 marksTitrimetric (Volumetric) Methods of Analysis

CAPE Chemistry Unit 2 · 2006 · Paper 2 · Question 5(e)(i)

0.005 moles of solid sodium hydroxide are added to the buffer solution in part (d). Assume no change in volume.

Find the new concentrations of sodium ethanoate and ethanoic acid.

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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(d)(ii)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…[5 marks]
  8. 5(e)(ii)Comment on the pH of the new solution and explain your answer.[2 marks]

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