Problem: Balance the following redox reaction by inserting the appropriate coefficients.H+ + CrO42- + NO2- → Cr3+ + H2O +NO3-

We’re being asked to balance the given oxidation-reduction reaction:

H⁺ + CrO₄^2– + NO₂^–→ Cr³⁺ + H₂O + NO₃^–

We assume that the redox is in acidic solution since H⁺ is present. When balancing redox reactions under acidic conditions, we will follow the following steps.

Step 1: Separate the whole reaction into two half-reactions.

Step 2: Balance the non-hydrogen and non-oxygen elements first.

Step 3: Balance oxygen by adding H₂O to the side that needs oxygen. (1 O: 1 H₂O)

Step 4: Balance hydrogen by adding H⁺ to the side that needs hydrogen. (1 H: 1 H⁺)