Question

Balance the following Re-Dox Reaction

Ammonium (NH4 + ) oxidation to nitrite (NO2 - ) using oxygen (O2) as the electron acceptor.

Answer 1

Answer – Given, ammonium (NH4 + ) oxidation to nitrite (NO2 - ) using oxygen (O2) as the electron acceptor.

We know the reaction

NH₄⁺ + O₂ -----> NO₂^-

Step 1) Assign the oxidation state to each element and write the two half reaction

   NH₄⁺ + O₂    ----->   NO₂^-

N= -3                           N = +3                         

O = 0                              O = -2

So O₂ get reduced and NH₄⁺ gets oxidized

   NH₄⁺ ----> NO₂^-………oxidation half reaction

     O₂(g) ----> NO₂^-……….reduction half reaction

Step 2) Balance the element other than O and H

    NH₄⁺ ----> NO₂^-

      O₂(g) + NO₂^- ----> NO₂^-

Step 3) Balance the O by adding 1 H₂O for 1 O

           NH₄⁺ + 2H₂O ----> NO₂^-

           O₂(g) + NO₂^- ----> NO₂^- + 2H₂O

Step 4) Balance the H by adding H⁺

           NH₄⁺ + 2H₂O ----> NO₂^- + 4H⁺

           O₂(g) + NO₂^- + 4H⁺ ----> NO₂^- + 2H₂O

Step 5) Balance the charge by adding electron

           NH₄⁺ + 2H₂O ----> NO₂^- + 4H⁺ + 2e^-

            O₂(g) + NO₂^- + 4H⁺ + 4e^- ----> NO₂^- + 2H₂O

Step 6) Balance the electron in both half reaction – Multiply by oxidation half by 2

           2 NH₄⁺ + 4 H₂O ----> 2 NO₂^- + 8H⁺ + 4e^-

           O₂(g) + NO₂^- + 4H⁺ + 4e^- ----> NO₂^- + 2H₂O

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           2 NH₄⁺ + O₂(g) + 2H₂O ---->2 NO₂^- + 4H⁺(aq)