10 FeSO3 + 6 KMnO4 + 14 H2SO4 → 6 MnSO4 + 5 Fe2(SO4)3 + 3 K2SO4 + 14 H2O
This is an oxidation-reduction (redox) reaction:
6 MnVII + 30 e- → 6 MnII (reduction)
10 SIV - 20 e- → 10 SVI (oxidation)
10 FeII - 10 e- → 10 FeIII (oxidation)
KMnO4 is an oxidizing agent, FeSO3 is a reducing agent, FeSO3 is a reducing agent.