According to this reaction:
3NO2^- + 8 H^+ + Cr2O7^-2 → 3NO3^- + 2Cr^+3 + 4 H2O
(1) 3 NO2^- → 3NO3^-, The oxidation state of nitrogen converted from +3 to +5
i.e oxidation process, ∴ NO2^- is reducing agent.
(2) Cr2O7^-2 → 2Cr^+3, The oxidation state of Cr converted from +6 to +3
i.e reduction process ∴ Cr2O7^-2 is an Oxidizing agent.
(3) H^+ → H2O, the oxidation state of Hydrogen is still +1, i.e No change (neither)
