Question

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

${\mathrm{Pb}}_3{\mathrm{O}}_4+8\mathrm{HCl}\to 3{\mathrm{PbCl}}_2+{\mathrm{Cl}}_2+4{\mathrm{H}}_2\mathrm{O}$

Answer 1

1. Redox reactions

Reactions that involve oxidation and reduction are called redox reactions. It involves the reaction between an oxidizing agent (reactant that undergoes reduction) and a reducing agent (reactant that undergoes oxidation). Oxidizing agent and reducing agent for a reaction can be identified by determining the change in the oxidation state of the reactants.

Oxidation is defined as the loss of electrons and reduction is the gain of electrons by a reactant.

2. Identifying the oxidizing and reducing agent

$$\begin{gathered} {\mathrm{Pb}}_3{\mathrm{O}}_4\left(\mathrm{s}\right)+8\mathrm{HCl}\left(\mathrm{g}\right)\to 3{\mathrm{PbCl}}_2\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Lead}\mathrm{Hydrochloric}\mathrm{Lead}\mathrm{Chlorine}\mathrm{Water} \\ \mathrm{tetraoxide}\mathrm{acid}\mathrm{chloride} \end{gathered}$$

The oxidation state of Lead has decreased from +6 in Lead tetraoxide $\left({\mathrm{Pb}}_3{\mathrm{O}}_4\right)$ to +2 in Lead chloride $\left({\mathrm{PbCl}}_2\right)$. Therefore, it undergoes reduction and is the oxidizing agent.

The oxidation state of Chlorine increase from -1 in Hydrochloric acid $\left(\mathrm{HCl}\right)$ to 0 in Chlorine $\left({\mathrm{Cl}}_2\right)$. Therefore, it undergoes oxidation and is the reducing agent.

Therefore, Lead tetraoxide is the oxidizing agent and Hydrochloric acid is the reducing agent.