Question

In which of the following reactions, chlorine undergoes disproportionation? \[ \begin{aligned} \text{I.} \quad & \text{Reaction with cold, dilute NaOH} \\ \text{II.} \quad & \text{Reaction with hot, concentrated NaOH} \\ \text{III.} \quad & \text{Reaction with } \mathrm{H_2S} \end{aligned} \] The correct answer is

• A. I, II only
• B. I, II, III
• C. III only
• D. II only \bigskip

Hint:

Chlorine undergoes disproportionation in alkaline medium: \[ \mathrm{Cl_2 \rightarrow Cl^- + ClO^-} \] (cold, dilute NaOH) \[ \mathrm{Cl_2 \rightarrow Cl^- + ClO_3^-} \] (hot, concentrated NaOH)

Answer 1

The Correct Option is A

Step 1: I: Cl₂ + cold dil NaOH → NaCl + NaOCl, disproportionation (0 to -1,+1). II: Cl₂ + hot conc NaOH → NaCl + NaClO₃, disproportionation (0 to -1,+5). III: Cl₂ + H₂S → HCl + S, only reduction (0 to -1). I & II only.

Step 2: Write the final answer. \(\boxed{\text{(A)}}\)