Answer:
a) Mn^2+ + 2OH- + H2O2 → MnO2 + 2H2O
b) 2Bi(OH)3 + 3SnO2^2- → 2Bi + 3SnO3^2- + 3H2O
c) Cr2O7^2- + 3C2O4^2- + 14H+ → 2Cr^3+ +7H2O + 6CO2
d) 2ClO3- + 2Cl- + 4H+ → Cl2 + 2H2O +2ClO2
e) 5 BiO3^- + 14 H+ + 2Mn^2+ → 5Bi^3+ + 7H2O + 2MnO4^-
Explanation:
<em>(a) Mn2 + H2O2 → MnO2 + H2O (in basic solution)</em>
Step 1: The half reactions
Oxidation: Mn2+ + 4OH- → MnO2 + 2H2O + 2e-
Reduction: H2O2 + 2e- + 2H2O → 2H2O + 2OH-
Step 2: Sum of both half reactions
Mn2+ + 4OH- + H2O2 → MnO2 + 2H2O + 2OH-
Step 3: the netto reaction
Mn^2+ + 2OH- + H2O2 → MnO2 + 2H2O
<em>(b) Bi(OH)3 + SnO2^2- → SnO3^2- + Bi (in basic solution)</em>
Step 1: The half reactions
Reduction: Bi(OH)3 + 3e- → Bi
Oxidation : Sno2^2- → SnO3^2- +2e-
Step 2: Balance the half reactions
2* (Bi(OH)3 + 3e- → Bi + 3OH-)
3* (Sno2^2- +2OH- → SnO3^2- +2e- + H2O)
Step 3: The netto reaction
2Bi(OH)3 + 3SnO2^2- → 2Bi + 3SnO3^2- + 3H2O
<em>(c) Cr2O7^2- + C2O4^2- → Cr^3+ + CO2 (in acidic solution)</em>
Step 1: The half reactions
Reduction: Cr2O7^2- + 6e- → 2Cr+
Oxidation : C2O4^2- → 2CO2 + 2e-
Step 2: Balance the half reactions
Cr2O7^2- + 6e- +14H+ → 2Cr+ +7H2O
3*(C2O4^2- → 2CO2 + 2e-)
Step 3: The netto reaction
Cr2O7^2- + 3C2O4^2- + 14H+ → 2Cr^3+ +7H2O + 6CO2
<em>(d) ClO3^- + Cl^− </em>→<em> Cl^2 + ClO^2 (in acidic solution)</em>
Step 1: The half reactions
Reduction: 2 ClO3^- + 10e- → Cl2
ClO3^- + e- → ClO2
2 Cl- + 2ClO3^- +8e- →2Cl2
Oxidation: 2Cl- → Cl2 + 2e-
Cl- → ClO2 + 5e-
Cl- +ClO3^- → 2ClO2 + 4e-
Step 2: Balance the reactions
2Cl- + 2ClO3^- + 8e- + 12H+ → 2Cl2 + 6H2O
2* (Cl- + ClO3^- + H2O → 2ClO2 + 4e- + 2 H+)
Step 3: The netto reaction
2ClO3^- + 2Cl- + 4H+ → Cl2 + 2H2O +2ClO2
<em>(e) Mn^2 + BiO3^− </em>→<em> Bi^3 + MnO^4− (in acidic solution)</em>
Step 1: The half reactions
Reduction: BiO3^- + 2e- → Bi^3+
Oxidation : Mn^2+ → MnO4^- +5e-
Step 2: Balanced the reactions
5* ( BiO3^- + 2e- + 6H+ → Bi^3+ + 3H2O)
2* ( Mn^2+ + 4H2O →MnO4^- + 5e- + 8H+)
Step 3: The netto reaction
5 BiO3^- + 14 H+ + 2Mn^2+ → 5Bi^3+ + 7H2O + 2MnO4^-
