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1 markAcid/Base Equilibria

CAPE Chemistry Unit 1 · 2010 · Paper 2 · Question 5(b)(i)

The acid dissociation constant (Ka) of ethanoic acid at 25 °C has a numerical value of 1.7 x 10⁻⁵. The equilibrium equation for the dissociation of ethanoic acid is CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq).

Write an expression for the acid dissociation constant (Ka) of ethanoic acid.

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  1. 5(a)(i)Define EACH of the following terms: pH[2 marks]
  2. 5(a)(ii)Define EACH of the following terms: Buffer solution[2 marks]
  3. 5(b)(ii)Calculate the equilibrium concentration of ethanoic acid in a solution that has a pH of 5.[4 marks]
  4. 5(c)(i)State the effect, on the equilibrium position of a buffer solution, of adding small amounts of H+(aq)[1 mark]
  5. 5(c)(ii)State the effect, on the equilibrium position of a buffer solution, of adding small amounts of OH-(aq).[1 mark]
  6. 5(d)Calculate the pH of this buffer solution. (Relative atomic mass: H = 1, C = 12, O = 16, Na = 23)[4 marks]

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