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2 marksAcid/Base Equilibria

CAPE Chemistry Unit 1 · 2007 · Paper 2 · Question 2(b)(i)

A chemist extracts the methanoic acid from 40 ants and adds water to make 25.00 cm³ of a Solution Y. He then titrates this solution with a 0.050 mol dm⁻³ standard solution of sodium hydroxide, NaOH(aq), a strong alkali, to determine the concentration of HCOOH in Solution Y.

Using Bronsted-Lowry theory, explain what is meant by a strong base.

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Other parts of this question

  1. 2(a)(i)Explain what is meant by the term 'weak acid'.[1 mark]
  2. 2(a)(ii)Write an expression for the dissociation constant, Kₐ, of methanoic acid.[1 mark]
  3. 2(b)(ii)Calculate the pH of the standard NaOH solution.[2 marks]
  4. 2(b)(iii)The concentration of methanoic acid in Solution Y is found to be 6.0 x 10⁻³ mol dm⁻³. Calculate the pH of Solution Y.[2 marks]
  5. 2(b)(iv)Suggest a suitable indicator for the titration between methanoic acid and sodium hydroxide.[1 mark]
  6. 2(b)(v)Sketch a graph to illustrate the changes in pH that take place during the titration.[4 marks]
  7. 2(c)Ant stings can be treated with baking soda, NaHCO₃. Suggest, with the aid of an equation, how baking soda helps to relieve the effect of the sting.[2 marks]

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