Chlorine disproportionation in alkaline medium

Steps:

• Reaction 1 with cold NaOH forms hypochlorite (ClO⁻) via Cl₂ + 2OH⁻ → ClO⁻ + Cl⁻ + H₂O, so Z is ClO⁻.
• Heating Z (ClO⁻) causes disproportionation to chlorate (ClO₃⁻) and chloride: 3ClO⁻ → ClO₃⁻ + 2Cl⁻.
• Match reaction 1 to options: only C and D have correct Cl₂ + 2OH⁻ → ClO⁻ + Cl⁻ + H₂O.
• Match reaction 2: only D has the standard 3ClO⁻ → ClO₃⁻ + 2Cl⁻ (no OH⁻ involved).

Why D is correct:

• Matches the established disproportionation formula for hot concentrated NaOH conditions, where hypochlorite converts to chlorate and chloride without additional OH⁻.

Why the others are wrong:

• A: Reaction 1 has incorrect 2Cl₂ stoichiometry for cold dilute conditions.
• B: Reaction 1 uses wrong 3Cl₂ + 3OH⁻, not standard for cold NaOH.
• C: Reaction 2 incorrectly adds 2OH⁻, resembling cold reaction instead of heating.

Final answer: D