Réponse:
Zn = Zn²⁺ + 2e⁻
[ Ag⁺ + e⁻ = Ag ] × 2
-------------------------------------
Zn + 2Ag⁺ → Zn²⁺ + 2Ag
2H⁺ + 2e⁻ = H₂
Fe = Fe²⁺ + 2e⁻
-------------------------------------
Fe + 2H⁺ → Fe²⁺ + H₂
I₂ + 2e⁻ = 2I⁻
2S₂O₃²⁻ = S₄O₆²⁻ + 2e⁻
---------------------------------------------
I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻