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2 marksTitrimetric (Volumetric) Methods of Analysis

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

Sodium hydrogen carbonate is often added to the water in swimming pools to act as a buffer.

Use the equation HCO₃⁻(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CO₃²⁻(aq) to explain how the aqueous hydrogen carbonate ion acts as a buffer.

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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(c)(i)Explain how the molecular structure of amino acids relates to their function as buffers in human blood.[3 marks]
  4. 5(c)(ii)State ONE industry in which buffers are used.[1 mark]
  5. 5(d)(i)Calculate the concentration of the sodium ethanoate solution in mol dm⁻³.[2 marks]
  6. 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]
  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]

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