Question

Identify the reducing agent and oxidizing agent in the following reactions:

${\mathrm{Fe}}_2{\mathrm{O}}_3+3\mathrm{CO}\to 2\mathrm{Fe}+3{\mathrm{CO}}_2$

Answer 1

1. Redox reactions

In a redox reaction between two reactants, one of the reactant will be an oxidizing agent and other will be the reducing agent. The oxidizing agent helps in the oxidation of other species by accepting electrons and thereby undergoes reduction. The reducing agent helps in the reduction of other species by donating electrons and thereby undergo oxidation.

In a redox reaction, therefore, the species undergoes an increase in oxidation state is the reducing agent and the species that undergoes a decrease in oxidation state is the oxidizing agent.

2. Identifying oxidizing and reducing agent

$$\begin{gathered} {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{CO}\left(\mathrm{g}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ \mathrm{Ferric}\mathrm{Carbon}\mathrm{Iron}\mathrm{Carbon} \\ \mathrm{oxide}\mathrm{monoxide}\mathrm{dioxide} \end{gathered}$$

In this reaction, the oxidation state of Iron $\left(\mathrm{Fe}\right)$ has reduced from +3 in Ferric oxide $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ to 0 in Iron. Therefore, it undergoes reduction and is the oxidizing agent.

The oxidation state of Carbon $\left(\mathrm{C}\right)$ increases from +2 in Carbon monoxide $\left(\mathrm{CO}\right)$ to +4 in Carbon dioxide $\left({\mathrm{CO}}_2\right)$. Therefore, it undergoes oxidation and is the reducing agent.

Thus, Carbon monoxide (CO) is the reducing agent and it has reduced ferric oxide $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ which acts as an oxidizing agent.