Answer to Question #236575 in General Chemistry for Mickayla

Question

Sodium thiosulfate, Na₂S₂O₃, is used as a ^"fixer^" in black and white photography. Identify the reducing agent in the reaction of thiosulfate with iodine.

2S₂O₃^2-(aq) + I₂(aq) → S₄O₆^2-(aq) + 2I^-(aq)

1. I₂(aq)
2. I^-(aq)
3. S₂O₃^2-(aq)
4. S₄O₆^2-(aq)

Answer 1

reducing agent in this reaction is thiosulfate (S₂O₃²⁻).

Balanced chemical reaction: 2S₂O₃²⁻(aq) + I₂(aq) → S₄O₆²⁻(aq) + 2I⁻(aq).

Reducing agent is element or compound who loose electrons in chemical reaction. Sulfur in thiosulfate change oxidation number from +2 to +5 tetrathionate anion (two sulfur atoms in the ion have oxidation state 0 and two atoms have oxidation state +5).