Answer to Question #112003 in General Chemistry for AChemStudent

Question

Balance the following in basic solution.

(a)Mn(OH)2(s) + O2(g) → MnO2(s)
Oxidation reaction
Reduction reaction
Net reaction

(b)In(s) + Cr2O72−(aq) → In(OH)3(s) + Cr(OH)4−(aq)
Oxidation reaction
Reduction reaction
Net reaction

(c)SO32−(aq) + Cu(OH)2(s) → SO42−(aq) + CuOH(s)
Oxidation reaction
Reduction reaction
Net reaction

(d)NO3−(aq) + H2(g) → NO(g)
Oxidation reaction
Reduction reaction
Net reaction

Answer 1

(a) Mn(OH)₂(s) + O₂(g) → MnO₂(s) 

Oxidation reaction

2Mn(OH)₂ + 4OH^- → 2MnO₂ + 4H₂O + 4e^-

Reduction reaction

O₂ + 4e^- + 4H₂O → 2H₂O + 4OH^- 

Net reaction

2Mn(OH)₂ + O₂ → 2MnO₂ + 2H₂O

(b) In(s) + Cr₂O₇²⁻(aq) → In(OH)₃(s) + Cr(OH)₄⁻(aq)

Oxidation reaction

2In + 6OH^- = 2In(OH)₃ + 6e^-

Reduction reaction

Cr₂O₇^2- + 6e^- + 7H₂O = 2Cr(OH)₄^- + 6OH^-

Net reaction

2In + Cr₂O7₂^- + 7H₂O → 2In(OH)₃ + 2Cr(OH)₄^-

(c) SO₃²⁻(aq) + Cu(OH)₂(s) → SO₄²⁻(aq) + CuOH(s)

Oxidation reaction

SO₃^2- + 2OH^- = SO₄^2- + 2e^- + H₂O

Reduction reaction

2Cu(OH)₂ + 2e^- = 2CuOH + 2OH^-

Net reaction

SO₃^2- + 2Cu(OH)₂ → SO₄^2- + 2CuOH + H₂O

(d) NO₃⁻(aq) + H₂(g) → NO(g)

Oxidation reaction

3H₂ + 6OH^- = 6H₂O + 6e^-

Reduction reaction

2NO₃^- + 6e^- + 4H₂O = 2NO + 8OH^-

Net reaction

3H₂ + 2NO₃^- = 2NO + 2H₂O + 2OH^-