Chemistry - Redox Reactions Question with Solution | TestHub

In the reaction $\text{Zn}+{\text{H}}_2{\text{SO}}_4\to {\text{ZnSO}}_4+{\text{H}}_2$, the oxidation state of Zn changes from $0$ to $+2$ and H changes from $+1$ to $0$. It is a redox reaction.

In the reaction ${\text{Al(OH)}}_3+3\text{HCl}\to {\text{AlCl}}_3+3{\text{H}}_2\text{O}$, the oxidation states of all elements remain the same (Al is $+3$, O is $-2$, H is $+1$, Cl is $-1$). It is an acid-base neutralization reaction, not a redox reaction.

In the reaction $\text{Mg}+1/2{\text{O}}_2\to {\text{Mg}}^{2+}+{\text{O}}^{2-}$, the oxidation state of Mg changes from $0$ to $+2$ and O changes from $0$ to $-2$. It is a redox reaction.

In the reaction ${\text{Fe}}_{(s)}+{\text{Cu}}_{(aq)}^{2+}\to {\text{Fe}}_{(aq)}^{2+}+{\text{Cu}}_{(s)}$, the oxidation state of Fe changes from $0$ to $+2$ and Cu changes from $+2$ to $0$. It is a redox reaction.

Answer: ${\text{Al(OH)}}_3+3\text{HCl}\to {\text{AlCl}}_3+3{\text{H}}_2\text{O}$