Gce Model Questions Vol1 2022 Chemistry Question 23

A 250.0 mL solution contains 0.0250 mol of \(\mathrm{Fe^{2+}}\). It is titrated with 0.0200 M \(\mathrm{KMnO_4}\) in acidic medium. The net reaction is \(\mathrm{MnO_4^- + 5 Fe^{2+} + 8 H^+ \rightarrow Mn^{2+} + 5 Fe^{3+} + 4 H_2O}\). (a) Calculate the volume of \(\mathrm{KMnO_4}\) solution required to reach the equivalence point. (b) If an additional 5.00 mL of the \(\mathrm{KMnO_4}\) solution is added beyond equivalence, determine the concentration of excess \(\mathrm{MnO_4^-}\) in the mixture. (c) The lake initially contains \(0.100\) M \(\mathrm{H_2SO_4}\). The titration consumes 8 mol of \(\mathrm{H^+}\) per mole of \(\mathrm{MnO_4^-}\). Calculate the pH of the solution after the excess \(\mathrm{KMnO_4}\) has been added.