Balance the redox reaction

Question

HNO₃^- + H₂S → NO + S + H₂O

Answer 1

HNO₃+ H₂S → NO + S + H₂O ... unbalanced

N on the left has ox.no. of 5+ and on the right it is 2+. It has been reduced

S on the left has ox. no. of 2- and on the right it is zero. It has been oxidized

We will use the half reaction method where we balance the oxidation and reduction half reactions separately, and then add them together to get the final balanced equation.

H₂S ==> S ... oxidation half reaction

H₂S ==> S + 2H⁺ ... balanced for S and H (using acid, H⁺)

H₂S ==> S + 2H⁺ + 2e- ... balanced for mass and charge = balanced oxidation half reaction

HNO₃ ==> NO ... reduction half reaction

HNO₃ ==> NO + 2H₂O ... balanced for N and O

HNO₃ + 3H⁺ ==> NO + 2H₂O ... balanced for N, O and H

HNO₃ + 3H⁺ + 3e- ==> NO + 2H₂O ... balanced for mass and charge = balanced reduction half reaction

Equalize electrons by multiplying oxidation reaction by 3 and reduction reaction by 2, to get

3H₂S ==> 3S + 6H⁺ + 6e-

2HNO₃ + 6H⁺ + 6e- ==> 2NO + 4H₂O

Add them together and combine/cancel like terms ...

3H₂S + 2HNO₃ ==> 3S + 2NO + 4H₂O ... BALANCED REDOX EQUATION

Answer 2