Question

If a substance gains oxygen during a reaction, it is being oxidized. If it loses oxygen, it is being reduced. Oxidation and Reduction always take place together, so that if one substance is oxidized, another is reduced. Using this idea, say which substance is oxidised and which substance is reduced in each reaction.
i) $\underset{\left(s\right)}{Mg}+\underset{\left(g\right)}{O_2}\to \underset{\left(s\right)}{2MgO}$
ii) $ZnO+C\to Zn+CO$
iii) $F{e}_2{O}_3+3CO\to 2Fe+3C{O}_2$
iv) $C{r}_2{O}_3+2Al\to 2Cr+A{l}_2{O}_3$

Answer 1

(i) Here $Mg$ gains oxygen, hence it is oxidized.

(ii) Here, $Zn$ loses while $C$ gains oxygen. Hence $Zn$ is reduced and $C$ is oxidized.

(iii) $Fe$ is losing and $C$ is gaining oxygen in the given reaction. Therefore, $Fe$ is reduced and $C$ is oxidized.

(iv) $Al$ gains and $Cr$ loses oxygen. Hence $Al$ is oxidized and $Cr$ is reduced.