A 25.0 mL aliquot of a solution containing Fe²⁺(aq),prepared during an assay of a pyrite ore,was titrated to a faint purple endpoint by 32.2 mL of 0.020 M KMnO₄(aq).What was the molarity of the Fe²⁺ solution? [The permanganate was reduced to Mn²⁺(aq).] A)0.13 M B)0.19 M C)0.26 M D)0.31 M E)0.47 M

Question

Quizplus · Accepted Answer

The balanced equation for the reaction is:8H+(aq) + 5Fe2+(aq) + MnO4-(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)From the stoichiometry of the balanced equation, we can see that 1 mole of MnO4- reacts with 5 moles of Fe2+. Therefore, the number of moles of Fe2+ in the 25.0 mL aliquot is:(32.2 mL KMnO4)(1 L/1000 mL)(0.020 mol/L KMnO4)(5 mol Fe2+/1 mol KMnO4) = 6.44 × 10^-4 mol Fe2+The molarity of the Fe2+ solution is:(6.44 × 10^-4 mol Fe2+)/0.0250 L = 0.26 MTherefore, the correct answer is C.

A 250 ML Aliquot of a Solution Containing Fe2+(aq),prepared During an an Assay

A 250 ML Aliquot of a Solution Containing Fe²⁺(aq),prepared During an an Assay