redox reaction of NO2 to NO3

Question

For a particular redox reaction, NO−2 is oxidized to NO−3 and Ag+ is reduced to Ag. Complete and balance the equation for this reaction in basic solution. Phases are optional.

balanced redox reaction:

Answer 1

So to balance any equation, the amount of each element must be the same on both sides of the equation. Not only that, but the charge (plus/minus) must also be the same. In this problem, we are given the two half-reactions. We can balance them separately, and then add them together.

NO₂^- ==> NO₃^- .. unbalanced oxidation reaction

NO₂^- + H₂O ==> NO₃^- .. balanced for N and O

NO₂^- + H₂O + 2OH^- ==> NO₃^- + 2H₂O .. balanced for N, O and H (by adding base, OH^-)

NO₂^- + H₂O + 2OH^- ==> NO₃^- + 2H₂O + 2e- .. balanced for N, O, H and charge

Ag⁺ + e- ==> Ag .. balanced for Ag and charge = balanced reduction reaction

Since 2 electrons were transferred in the oxidation reaction, and only 1 electron was transferred in the reduction reaction, we need to multiply the reduction reaction by 2 and then add the two together:

2Ag⁺ + 2e- ==> 2Ag

NO₂^- + H₂O + 2OH^- ==> NO₃^- + 2H₂O + 2e-

-------------------------------------------------------------- add together and combine/cancel like terms......

2Ag⁺ + NO₂^- + 2OH^- ==> 2Ag + NO₃^- + H₂O .. balanced redox equation