4 H2SO4 + 2 KNO2 + 6 CrSO4 → 4 H2O + K2SO4 + N2 + 3 Cr2(SO4)3
This is an oxidation-reduction (redox) reaction:
6 SII - 24 e- → 6 SVI (oxidation)
2 NIII + 6 e- → 2 N0 (reduction)
6 CrVI + 18 e- → 6 CrIII (reduction)
CrSO4 is a reducing agent, KNO2 is an oxidizing agent, CrSO4 is an oxidizing agent.