Question

In the reaction $\mathrm{Mg}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{MgCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$, what role does Magnesium play?

Answer 1

Reducing agent:-

1. A reducing agent is basically a substance which can be oxidized by losing some of its electrons.
2. It acts as the electron donor.
3. Here, the oxidation state also increases.
4. In this redox reaction:- $\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{{\mathrm{MgCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$ , Magnesium metal is being oxidized to magnesium cations${\mathrm{Mg}}^{2+}$.
5. Whereas Hydrogen is being reduced to $\left({\mathrm{H}}^{+}\right)$ then to Hydrogen gas ${\mathrm{H}}_2$.
6. Magnesium goes from an oxidation state of 0 which is on the reactant's side to an oxidation state of +2 on the product's side, which shows it is being oxidized.
7. Hydrogen goes from the oxidation state of +1 on the reactant's side to an oxidation state of 0 on the product's side, showing that it is being reduced.
8. So, Magnesium $\left(\mathrm{Mg}\right)$ is acting as a reducing agent as it reduces Hydrogen to Hydrogen gas while being itself oxidized in the process.

Therefore, In the reaction$\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{{\mathrm{MgCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$, Magnesium plays the role of the Reducing agent.