4 Na + 2 KNO3 → 2 KO2 + 2 Na2O + N2
This is an oxidation-reduction (redox) reaction:
4 Na0 - 4 e- → 4 NaI (oxidation)
2 NV + 10 e- → 2 N0 (reduction)
4 O-II - 6 e- → 4 O-1/2 (oxidation)
Na is a reducing agent, KNO3 is an oxidizing agent, KNO3 is a reducing agent.