Question

Is the dissolution of a solid metal in an acidic solution an example of a `"redox reaction?"`

Answer 1

`Zn(s) + 2HCl(aq) rarr ZnCl_2(aq) + H_2(g)uarr`

The metal is oxidized, and the hydrogen ion is reduced.

Explanation:

For the oxidation of `"Zn"`:

`Zn(s) rarr Zn^(2+) + 2e^-`; `"oxidation (i)"`

For the reduction of `"hydronium ion"`:

`H^(+) + e^(-) rarr 1/2H_2(g)`; `"reduction (ii)"`

We add these equations together such that electrons do not appear in the equation: `(i) +2xx(ii):`

`Zn(s) +2H^(+) rarr Zn^(2+) + H_2(g)uarr`

We would repeat this for iron metal and sulfuric acid, except that sulfuric acid is a non-oxidizing acid under normal circumstances, and the question SHOULD have been asked with respect to hydrochloric acid or nitric acid. Iron filings will react with `HCl` in precisely the same stoichiometry as zinc:

`Fe(s) + 2HCl(aq) rarr FeCl_2(aq) + H_2(g)uarr`