Question

Consider the following decomposition reaction
$2 KClO _{3} \longrightarrow 2 KCl +3 O _{2}$
In the above reaction,

• A. potassium is undergoing oxidation
• B. chlorine is undergoing reduction
• C. oxygen is reduced
• D. None of the species are undergoing oxidation or reduction

Answer 1

Answer: (B)

$\overset{+1+5-2}{2 KClO )_{3}} \longrightarrow \overset{+1-1}{2 KCl} +3 \overset{0}{O _{2}}$
(a) The oxidation number of $K$ does not change, thus $K$ undergoes neither reduction nor oxidation.
(b) The oxidation number of chlorine decreases from $+5$ in $KClO _{3}$ to $-1$ in $KCl$, hence $Cl$ undergoes reduction.
(c) Since, oxidation number of oxygen increases from $-2$ in $KClO _{3}$ to 0 in $O _{2}$, so oxygen is oxidised.
(d) This statement is not correct because $Cl$ is undergoing reduction and $O$ is undergoing oxidation.
Therefore, statement (b) is true about the given reaction.