When Cl2 gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from
- zero to +1 and zero to −5
- zero to −1 and zero to +5
- zero to −1 and zero to +3
- zero to +1 and zero to −3
Answer
(2) zero to −1 and zero to +5
Solution
3Cl2+6NaOH(hot, conc.) 5NaCl+NaClO3+3H2O
In NaCl, Cl = −1 ; in NaClO3, 1+x+3(-2)=0 x=+5
Chlorine disproportionates: 0 → −1 and 0 → +5.
Answer: (2)