1. Do you know how to write a half equation or an ionic equation? It seems you've just started chemistry.
These are the steps to write a half equation.
1) Write the substance and its oxidized or reduced states.
2) Balance the oxygen atoms by adding H2O
3) Balance the hydrogen atoms by adding H+ (only in acidic solution)
4) Balance charges by adding e-
MnO4- ---> Mn2+ (step 1)
MnO4- ---> Mn2+ + 4H20 (step 2)
MnO4- + 8H+ ---> Mn2+ + 4H20 (step 3)
MnO4- + 8H+ + 5e- ---> Mn2+ + 4H20 (step 4)
You try doing the same steps for C2042- and combine the final equations by eliminating e- to get the net ionic equations.
2. You have to write a net ionic equation between Fe2+ and MnO4-, and to find the stoichiometric coefficients.
3a. You have the volume and amounts of KMnO4 solution, you can get the moles of MnO4- consume.
3b. Same as question 2. Same stoichiometric coefficients
3c. Once you get the amounts of Fe2+, you can get the mass.
and welcome! If you still don't understand, let me know