Chemistry Redox Reactions

1.
Half equations :
Cr2O3(s) + 10OH^-(aq) → 2CrO4^2-(aq) + 5H2O(l)+ 6e^- ... (*)
OCl^-(aq) + H2O(l) + 2e^- → Cl^-(aq) + 2OH^-(aq) ...(#)

(*) + 3(#), and cancel 3H2O(l) and 6OH^-(aq) on the both sides.
Overall equation :
Cr2O3(s) + 3OCl^-(aq) + 4OH^-(aq)→ 2CrO4^2-(aq) + 3Cl^-(aq) + 2H2O(l)

n = 6


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2.
Half equations :
Sn(OH)3^-(aq) + 3OH^-(aq) → Sn(OH)6^2-(aq) +2e^- ... (*)
Bi(OH)3(s) + 3e^- → Bi(s) + 3OH^-(aq) ... (#)

3(*) + 2(#), and cancel 6OH^-(aq) on the both sides.
Overall equation :
3Sn(OH)3^-(aq) + 2Bi(OH)3(s)+ 3OH^-(aq) → 2Bi(s) + 3Sn(OH)6^2-(aq)

n = 6


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3.
Half equations :
MnO4^-(aq) + 2H2O(l) + 3e^- → MnO2(s) +4OH^-(aq) ... (*)
S^2-(aq) → S(s) + 2e^- ... (#)

2(*) + 3(#).
Overall equation :
2MnO4^-(aq) + 3S^- + 4H2O(l)→ 2MnO2(s) + 3S(s) + 8OH^-(aq)

n = 6


*****
4.
C2O4^2-(aq) + 4OH^-(aq) → 2CO3^2-(aq) +2H2O(l) + 2e^- ... (*)
MnO4^-(aq) + 2H2O(l) + 3e^- → MnO2(s) +4OH^-(aq) ... (#)

3(*) + 2(#), and cancel 8OH^-(aq) and 4H2O(l) on the both sides.
3C2O4^2-(aq) + 2MnO4^-(aq)+ 4OH^-(aq) → 2MnO2(s) + 6CO3^2-(aq) + 2H2­O(l)

n = 6