HCl + KMnO4 + NaNO2 → H2O + KCl + NaNO3 + MnCl2
6 HCl (aq) + 2 KMnO4 (aq) + 5 NaNO2 (aq) → 3 H2O (l) + 2 KCl (aq) + 5 NaNO3 (aq) + 2 MnCl2 (aq)
This is an oxidation-reduction (redox) reaction:
2 MnVII + 10 e– → 2 MnII (reduction)
5 NIII – 10 e– → 5 NV (oxidation)
KMnO4 is an oxidizing agent, NaNO2 is a reducing agent.