Balance this ionic equation for a redox reaction, using only whole number coefficients?

Question

? MnO4^- (aq) + ? Fe^+2 (aq) + ? H3O^+ (aq) + ? Fe^+3 (aq) H2O (l)

What is the coefficient for Fe^+2 in the balanced equation?

Please provide me the solution for this type of question (even though I understand how to balance, but can't do nothing with this sort of problem)

Also another similar problem

? Cr2O7^-2 + ?H2S (aq) -> ? Cr^+3 (aq) + ?S(s)

Answer 1

Kyle, the reactions are supposed to really occur.  In the first, you have no Mn-related compound in your reactants.   Assuming the second rxn works, we need to know if it is an acid-side or base-side rxn.  That is because the oxygen in the Cr2O7 has to be accounted for on the product side.  In acid, the product is H2O; in base, the product is OH-.