WAEC Chemistry 2020 Paper

Concept:The sum of oxidation states in a neutral compound is zero.Explanation:In $\mathrm{NaClO}_3$, sodium has an oxidation state of $+1$.Oxygen usually has an oxidation state of $-2$, and there are three oxygen atoms.So, total contribution of oxygen is $3 \times (-2) = -6$.Let the oxidation state of chlorine be $x$.Using the rule: $+1 + x + (-6) = 0$Thus, $x - 5 = 0$, giving $x = +5$.Answer:The oxidation state of chlorine is $+5$.Correct option: C. $+5$