The metal content of iron in ores can be determined by a redox procedure in which the sample is first oxidized with br2 to convert all the iron to fe3+ and then titrated with sn2+ to reduce the fe3+ to fe2+.

the balanced equation is: 2fe3+(aq) + sn2+(aq) -> 2fe2+(aq) + sn4+(aq)

what is the mass percentage fe in a 0.1875g sample if 13.28 ml of 0.1015 m sn2+ solution is needed to titrate the fe3+?