Question

Complete and balance the following equations, and identify the oxidation and reducing agents:

a) Cr₂O₇^2-(aq) + I^- (aq) → 2Cr ⁺³ + IO₃^- (acidic solution)

b) MnO₄^-(aq) + CH₃OH(aq) →Mn²⁺(aq) + HCOOH(aq) (acidic solution)

c) I₂(s) + ClO^- (aq) → IO₃^- (aq) +Cl^- (aq) (acidic solution)

d) As₂O₃ (s) + 2NO₃^-(aq) → 2H₃AsO₄ +N₂O₃ (acidic solution)

e) MnO₄^- + H₂O +Br^- → 2MnO₂ + 2OH^- + BrO₃^- (basic solution)

f) Pb(OH)₄^2- (aq) + ClO^- (aq) → PbO₂(s) + Cl ^– (aq) (basic solution)

One Class Solution:-

1. Cr₂O₇^2- + I^- + → Cr ⁺³ + IO₃^- (acidic solution)

_{+6 +3}

Cr₂O₇^2-→ Cr ⁺³ REDUCTION

_{-1 +5}

I^-→ IO₃^- OXIDATION

Cr₂O₇^2- +14 H⁺ +6 e- → 2Cr ⁺³ + 7H₂O

I^- + 3H₂O → IO₃^- + 6H⁺+ 6e-

Cr₂O₇^2- + 14 H⁺+ I^- + 3H₂O → 2Cr ⁺³ + IO₃^- + 6H⁺ + 7H₂O

+6OH^- → 6OH^-

Cr₂O₇^2- + 8H⁺+ I^- + 3H₂O → 2Cr ⁺³ + IO₃^- + 7H₂O

b)MnO₄^- + CH₃OH →Mn²⁺ + HCOOH (acidic solution)

+7 +2

MnO₄^- →Mn²⁺ REDUCTION

-2 +2

CH₃OH → HCOOH OXIDATION

MnO₄^- + 8H⁺ + 5e- → Mn²⁺ + 4H₂O ∕^. 4

CH₃OH + H₂O → HCOOH + 4H⁺ +4 e- ∕ ^.5

4MnO₄^- + 32H⁺ + 20e-+ 5CH₃OH + 5H₂O→ 4Mn²⁺ + 5HCOOH + 20H⁺ +20 e- + 16H₂O

+20OH^- → 20OH^-

4MnO₄^- + 12H⁺ + 5CH₃OH + → 4Mn²⁺ + 5HCOOH + 11H₂O

c)I₂ + OCl^- → IO₃^- + Cl^- (acidic solution)

0 +5

I₂→ IO₃^- OXIDATION

+1 -1

OCl^- → Cl^- REDUCTION

0 +5

I₂ + 3H₂O → 2IO₃^- + 6H⁺ + 5e- / 2

+1 -1

ClO^- + H⁺ + 2 e-→ Cl^- + H₂O /5

2I₂ + 6H₂O + 5ClO^- + 5H⁺ + 10 e- → 4IO₃^- + 12H⁺ + 10e- + 5Cl^- + 5H₂O

+5H⁺ → +5H⁺

2I₂ + 6H₂O + 5ClO^- → 4IO₃^- + 7H⁺ + 5Cl^- + 5H₂O

d)As₂O₃ + NO₃^-→ H₃AsO₄ + N₂O₃ (acidic solution)

+3 +5

As₂O₃→2H₃AsO₄ OXIDATION

+5 +3

2NO₃^-→ N₂O₃ REDUCTION

As₂O₃ + 5H₂O → 2H₃AsO₄ + 4H⁺+ 4e- /4

2NO₃^- + 6H⁺ +4e- → N₂O₃ + 3H₂O /4

As₂O₃ + 2NO₃^- + 6H⁺ +4e- +5H₂O → 2H₃AsO₄ + 4H⁺+ 4e- + N₂O₃ + 3H₂O

+4 OH → +4OH

As₂O₃ + 2NO₃^- + 2H⁺ +2H₂O → 2H₃AsO₄ + N₂O₃

e)MnO₄^- + Br^- → MnO₂ + BrO₃^- (basic solution)

+7 +4

MnO₄^- + 2H₂O +3e- → MnO₂ + 4OH^- /2

-1 +5

Br^- + 6OH^- → BrO₃^-+ 3H₂O + 6e- /1

2MnO₄^- + 4H₂O +6e- + Br^- + 6OH^- → 2MnO₂ + 8OH^-+ BrO₃^-+ 3H₂O + 6e-

+ 6 H⁺ → + 6 H⁺

2MnO₄^- + H₂O +Br^- → 2MnO₂ + 2OH^-+ BrO₃^-

f) Pb(OH)₄^2- + ClO^- → PbO₂ + Cl –

+2 +4

Pb(OH)₄^2- → PbO₂ + H₂O +2 e- oxidation/1

+1 -1

ClO^- + H₂O +2 e- → Cl ^– +2 OH^- reduction /1

Pb(OH)₄^2- + ClO^- + H₂O + 2 e- → PbO₂ + H₂O + Cl ^– + 2OH^- + 2 e-

+H⁺ → +H⁺

Pb(OH)₄^2- + ClO^- → PbO₂ + Cl ^– + 2OH^-+H₂O