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3 marksAcid/Base Equilibria

CAPE Chemistry Unit 1 · May/June 2026 · Paper 2 · Question 2(d)(iv)

Dissociation constant of hydrofluoric acid, HF, is 5.62 * 10^-4 mol dm^-3.

A student performs a titration, adding 0.10 mol dm^-3 sulfuric acid to 25 cm³ of 0.10 mol dm^-3 sodium hydroxide solution. Using the axes in Figure 1, sketch a graph to show the changes in pH which occur during the titration. Indicate the pH at which the equivalence point is reached.

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Other parts of this question

  1. 2(a)Define the term 'rate of a reaction'.[2 marks]
  2. 2(b)(i)With reference to the experiment number used, deduce the order of the reaction with respect to Substance A and Substance B.[4 marks]
  3. 2(b)(ii)Write the rate equation for the reaction between A and B.[1 mark]
  4. 2(b)(iii)Using the rate equation from (b)(ii), calculate the numerical value of the rate constant k, stating its unit.[2 marks]
  5. 2(b)(iv)Using the rate equation from (b)(ii), suggest a mechanism for the reaction between A and B.[2 marks]
  6. 2(c)Define the term 'acid' using the Bronsted-Lowry theory.[1 mark]
  7. 2(d)(i)Write the equation for the dissociation of hydrofluoric acid in aqueous solution.[2 marks]
  8. 2(d)(ii)Write the expression for the dissociation constant for hydrofluoric acid.[1 mark]
  9. 2(d)(iii)Calculate the pH of 0.10 mol dm^-3 hydrofluoric acid.[3 marks]
  10. 2(e)(i)Define standard cell potential.[2 marks]
  11. 2(e)(ii)Define standard electrode potential.[2 marks]
  12. 2(f)Describe, in detail, the steps that could be used to determine the standard electrode potential of copper in the laboratory.[5 marks]

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