Question

Balance the following equation for reactions occurring in acidic solution: MnO4__ + H2S Mn2+ + S

Answer 1

Given reaction MnO₄^- + H₂S -------------------> Mn²⁺ + S

1) Oxidation half reaction 1) Reduction half reaction

   MnO₄^-  -------------------> Mn²⁺   H₂S -------------------> S

2) Balance the oxygen atoms by adding H2O 2) No oxygen atoms are there, so no balance is required

MnO₄^-  -------------------> Mn²⁺ + 4H2O

3)  Balance the hydrogen atoms by adding H+ 3) Balance the hydrogen atoms by adding H+

   MnO₄^- + 8H+ -------------------> Mn²⁺ + 4H2O   H₂S ------------------->  S + 2H+

4) Balance the charge by adding electrons 4) Balance the charge by adding electrons

    MnO₄^- + 8H+ + 5e- -----------> Mn²⁺ + 4H2O H₂S ------------------->  S + 2H+ + 2e-

5) Multiply the oxidation half reaction with 2 and reduction half recation with 5

   2MnO₄^- + 16H+ + 10 e- -----------> 2Mn²⁺ + 8H2O

  5H₂S -------------------> 5S + 10H+ + 10e-

6) Cancel the electrons on both sides and writethe sum of two reactions

  2MnO₄^- + 16H+ +  5H₂S -----------> 2Mn²⁺ + 8H₂O +  5S + 10H+

7) Cancel 10 H+ on both sides

  2MnO₄^- + 6H⁺ +  5H₂S -----------> 2Mn²⁺ + 8H₂O +  5S

Therefore, balanced equation is

2MnO₄^-  +  5H₂S + 6H⁺   -----------> 2Mn²⁺ + 8H₂O +  5S