We are being asked to balance the given oxidation-reduction reaction. The reaction is under acidic conditions. 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+)
Step 5: Balance the charges: add electrons to the more positive side (or less negative side)
Step 6: Balance electrons on the two half-reactions
Step 7: Get the overall reaction by adding the two reactions.
Balance the redox reaction under acidic conditions:
NO2-(aq) + Cr2O72-(aq) → Cr3+(aq) + NO3-(aq)
*Before balancing the redox reaction:
•ignore H+, OH-, and H2O in the starting reaction
Balance the following reaction:
NO2-(aq) + Cr2O72-(aq) → Cr3+(aq) + NO3-(aq) (acidic solution)