Question

Balance the following equation in acidic solution using the lowest possible integers and give the coefficient of H+. MnO4-(aq) + H2S(g) → Mn2+(aq) + HSO4-(aq)

Answer 1

Mn in MnO4- has oxidation state of +7
Mn in Mn+2 has oxidation state of +2
So, Mn in MnO4- is reduced to Mn+2
This means MnO4- is oxidising agent

S in H2S has oxidation state of -2
S in HSO4- has oxidation state of +6
So, S in H2S is oxidised to HSO4-
This means H2S is reducing agent





Reduction half cell:
MnO4- + 5e- --> Mn+2
Oxidation half cell:
H2S --> HSO4- + 8e-
Balance number of electrons to be same in both half reactions

Reduction half cell:
8 MnO4- + 40e- --> 8 Mn+2
Oxidation half cell:
5 H2S --> 5 HSO4- + 40e-
40 electrons are being transferred in the reaction

Lets combine both the reactions.
8 MnO4- + 5 H2S --> 8 Mn+2 + 5 HSO4-
Balance Oxygen by adding water

8 MnO4- + 5 H2S --> 8 Mn+2 + 5 HSO4- + 12 H2O

Balance Hydrogen by adding H+
8 MnO4- + 5 H2S + 19 H+ --> 8 Mn+2 + 5 HSO4- + 12 H2O
This is balanced chemical equation in acidic medium
Answer:

8 MnO₄^- + 5 H₂S + 19 H⁺ --> 8 Mn²⁺ + 5 HSO₄^- + 12 H₂O

Coefficient of H+ is 19