Question

Identify the substance oxidized, reduced, oxidizing agent and reducing agent for each of the following reactions:
$\text{P}{{\text{b}}_{\left( \text{s} \right)}}+\text{Pb}{{\text{O}}_{2\left( \text{s} \right)}}+2{{\text{H}}_{2}}\text{S}{{\text{O}}_{4\left( \text{aq} \right)}}\to 2\text{PbS}{{\text{O}}_{4\left( \text{s} \right)}}+2{{\text{H}}_{2}}{{\text{O}}_{\left( \text{l} \right)}}$

Answer 1

Hint: To solve these types of questions we have to find out which species is getting reduced and which is getting oxidized. The species whose oxidation state is decreasing is the one getting reduced and the species whose oxidation state is increasing is getting oxidized. The species getting oxidized is the reducing agent and the species getting reduced is oxidizing agent.

Complete answer:
Oxidation is the process of loss of electrons during a reaction by a molecule, atom or ion. It occurs when the oxidation state of a molecule, atom or ion is increased. The process opposite to this is called reduction, which occurs when there takes place a gain of electrons or the oxidation state of a species decreases.

An oxidising agent is a substance that has the ability to oxidize other substances or to accept their electrons.
Reducing agent is the name given to an element or compound that loses an electron to an electron recipient in a redox chemical reaction. A reducing agent is thus oxidized when it loses electrons in a reaction. Reducing agents reduce the oxidizing agents.
$\text{P}{{\text{b}}_{\left( \text{s} \right)}}$has oxidation state as 0
$\text{Pb}{{\text{O}}_{2\left( \text{s} \right)}}$here Pb has oxidation state as $+4$
$\text{PbS}{{\text{O}}_{4\left( \text{s} \right)}}$here Pb has oxidation state as $+2$
So, $P{{b}^{0}}\to P{{b}^{2+}}$and $P{{b}^{4+}}\to P{{b}^{2+}}$

Hence,
Oxidized specie is $\text{P}{{\text{b}}_{\left( \text{s} \right)}}$
Reduced specie is $\text{Pb}{{\text{O}}_{2\left( \text{s} \right)}}$
Oxidizing agent is $\text{PbS}{{\text{O}}_{4\left( \text{s} \right)}}$
Reducing agent is $\text{P}{{\text{b}}_{\left( \text{s} \right)}}$

Note: A redox reaction can be defined as a chemical reaction in which electrons are transferred between the two reactants participating in it. This transfer of electrons can be identified by observing the changes taking place in the oxidation states of the reacting species.