4 KMnO4 (aq) + 6 H2SO4 (aq) → 4 MnSO4 (aq) + 2 K2SO4 (aq) + 5 O2 (g) + 6 H2O (l)
This is an oxidation-reduction (redox) reaction:
4 MnVII + 20 e- → 4 MnII (reduction)
10 O-II - 20 e- → 10 O0 (oxidation)
This is a gas evolution reaction, O2 is the formed gas.