Question

Below are the reduction half reactions for chemolithoautotrophic nitrification, where ammonia is a source of electrons and energy and oxygen is the terminal electron acceptor.

NO₂^- + 6e^- -> NH₄⁺ (-0.41 volts)

O₂ + 4e^- -> 2H₂O (+0.82 volts)

If you balance and combine the reactions so that 82 molecules of NH₄⁺ are oxidized to NO₂^-, how many molecules of O₂ will be reduced to H₂O?

Answer 1

You need to first balance the oxidation half and the reduction half to get a completely balanced redox reaction in this case.

The balance require the steps in each side

a. balance the atoms is getting oxidized or reduced

b. balance electrons

c. balance number of O atoms

d. balance number of H atoms

e. after balancing both halves, you multiply them by a factor so that the electrons get canceled out.

See attachement for details.