CSEC Chemistry · May/June 2008 · Paper 2 · Question 1(a)(iv)

A strong acid-base titration is performed, and pH changes are measured using a pH meter to determine the end point. The end point is expected to be a sharp pH change at 7.0. Figure 1 shows ten pH readings from an experiment where 20.0 cm³ of 0.005 mol dm⁻³ sulphuric acid is titrated with sodium hydroxide of unknown concentration. Reading I is the initial pH of the sulphuric acid, and readings II to X are pH values after adding various volumes of sodium hydroxide, as indicated in Figure 1.

Use the graph to determine the volume of sodium hydroxide which reacts completely with the 20 cm³ of 0.005 mol dm⁻³ sulphuric acid.

This question uses a figure or table from the paper — you'll see it when you practise.