Question

If chlorine gas is pased through a hot NaOH solution, two changes are observed in the oxidation number of chlorine during the reaction.These are _____________and ___________.

• A. 0 to + 1
• B. 0 to + 3
• C. 0 to -1
• D. 0 to + 5

Answer 1

Answer: (C), (D)

0 to + 5

Reaction of $C{l}_2$ with hot NaOH solution.

When $C{l}_2$ gas is passed through hot and conc. NaOH solution, sodium chloride and sodium chlorate is produced.

$3C{l}_2+6NaOH\to 5NaCl+NaCl{O}_3+3H_{2}O$

Sodium
Chlorate
Calculation of change in oxidation number

In $C{l}_2$ (Chlorine), Cl has zero oxidation state. In NaCl, Chlorine has an oxidation state of -1 sodium has an oxidation state of + 1.
In $NaCl{O}_3$ sodium has an oxidation state of +1.
Let, the oxidation state of $ClinNaCl{O}_3$ be x.

$1+x+3(-2)=0$

$1+x-6=0$

$x=+5$

Oxidation number of $Cl$ change from $0to-1inNaCl$ formation and 0 to + 5 in $NaCl{O}_3$ formation.

Hence, option (A) and (C) are the correct answer.