SnS + 2 KMnO4 + 4 H2SO4 → Sn(SO4)2 + 2 MnSO4 + K2SO4 + 4 H2O
This is an oxidation-reduction (redox) reaction:
2 MnVII + 10 e- → 2 MnII (reduction)
S-II - 8 e- → SVI (oxidation)
SnII - 2 e- → SnIV (oxidation)
KMnO4 is an oxidizing agent, SnS is a reducing agent, SnS is a reducing agent.