H2SO4 (aq) + 2 KNO3 (aq) + 3 H2O2 (aq) → 4 H2O (l) + 3 O2 (g) + K2SO4 (aq) + 2 NO (g)
This is an oxidation-reduction (redox) reaction:
2 NV + 6 e- → 2 NII (reduction)
6 O-I - 6 e- → 6 O0 (oxidation)
KNO3 is an oxidizing agent, H2O2 is a reducing agent.
This is a gas evolution reaction, O2 and NO is the formed gas.