Potassium permanganate solution is commonly used to determine the amount of oxalate ion,
CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
Potassium permanganate solution is commonly used to determine the amount of oxalate ion, C2O42−, present in a sample. In the titration medium, the reaction takes place in acidic solution, and the relevant redox process converts permanganate into an aqueous manganese(II) ion while oxalate is oxidized to carbon dioxide gas.
(a) Determine the oxidation number of manganese in MnO4− and in Mn2+, and the oxidation number of carbon in C2O42− and in CO2.
(b) Write separate balanced half-equations for the reduction of MnO4− and the oxidation of C2O42− in acidic solution, including electrons and any necessary H+ or H2O terms.
(c) Combine the half-equations from part (b) to obtain the overall balanced ionic equation for the titration reaction in acidic medium. Express each coefficient as the lowest possible whole number.
(d) From your balanced equation, state the number of moles of electrons transferred per mole of oxalate ion consumed.
(e) A 25.00mL aliquot of 0.0200MKMnO4 is required to reach the endpoint when titrating an unknown oxalate sample under the conditions described. Calculate the number of moles of oxalate originally present in the sample.