Am I headed in the right direction.

Question

Sn + MnO4- --> Sn2+ + Mn2+

Sn --> Sn2+ + 2e-
5e + 8H + MnO4- --> Mn2+ + 4H2O
If Im right what is the whole number that Im multiplying by

Answer 1

Both half reactions are right. Electrons gained by one half reaction must get them from somewhere which is just another way of saying electrons lost must equal electrons gained. The only number for both 2 and 5 is 10, so multiply one half cell by 5 and the other by 2, then add them, then cancel anything common to both sides.