The iron content in ores can be determined by titrating a sample with a solution of potassium permanganate. The ore is first dissolved in hydrochloric acid, forming iron (II) ions, which react with permanganate ions according to the following net-ionic reaction:
MnO4- (aq) + 5 Fe 2+ + 8H + (aq) → Mn 2+ (aq) + 5 Fe 3+ (aq) + 4 H 2O (l)
A sample of ore of mass 0.202g was dissolved in hydrochloric acid, and the resulting solution needed 16.7 mL of 0.0108 M KMnO4(aq) to reach the stoichiometric point.
What mass of iron (II) ions are present?
What is the mass percentage of iron in the sample of ore?