Q. When Cl₂ gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from
A) Zero to +1 and zero to −3
B) Zero to +1 and zero to −5
C) Zero to −1 and zero to +5
D) Zero to −1 and zero to +3
Explanation
[Solution from source] With hot concentrated NaOH, chlorine disproportionates: 3Cl₂ + 6NaOH → 5NaCl + NaClO₃ + 3H₂O. Chlorine goes from 0 to −1 in chloride and 0 to +5 in chlorate. The change 0 to +1 (hypochlorite) occurs with cold dilute NaOH. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.