In many residential water systems, the aqueous Fe3+ concentration is high enough to stain sinks and turn drinking water light brown. The iron content is analyzed by first reducing the Fe3+ to Fe2+ and then titrating with MnO4- in acidic solution.

Fe2+(aq) + MnO4-(aq) ? Mn2+(aq) + Fe3+(aq)

Balance the skeleton reaction of the titration step. (Use the lowest possible coefficients. Include states-of-matter under SATP conditions in your answer.)