Identify the oxidizing agent (oxidant) in the following reactions.
                                  $CuO + {H_2}\xrightarrow{{}}Cu + {H_2}O$

Hint: We know that if the oxidation state of the species decreases then it is getting reduced and it is called oxidizing agent. If the oxidation state of the species is increasing then the species is getting oxidized and it is called a reducing agent.

Complete step by step answer: We know, oxidation is the process in which electrons of a molecule, atom or ion are lost during a reaction. Oxidation occurs when the oxidation state of the species is increased.
The substance which oxidizes other substances (by removal of hydrogen or addition of oxygen) and itself gets reduced (addition of hydrogen or removal of oxygen) is called oxidizing agent.
The given reaction is,
$CuO + {H_2}\xrightarrow{{}}Cu + {H_2}O$
In the above reaction, cupric oxide \[\left( {CuO} \right)\] acts as an oxidizing agent because it oxidizes hydrogen to form water and copper.

Note: We remember that the reduction is an opposite process of oxidation. If the electrons are gained by a molecule, atom or ion then it is called reduction it occurs when the oxidation state of the species is decreased.
If an element or a compound loses an electron to an electron recipient in a redox chemical reaction then it is called a reducing agent. Thus, the reducing agent is the one which oxidized in a reaction. We also remember the reducing agent reduces the oxidizing agent.
Consider the reaction,
$Pb\left( s \right) + Pb{O_2}\left( s \right) + 2{H_2}S{O_4}\left( {aq} \right)\xrightarrow{{}}2PbS{O_4}\left( s \right) + 2{H_2}O\left( l \right)$
In the above reaction, the oxidation state of lead$\left( {Pb} \right)$ is zero and the oxidation state of lead in $\left( {Pb{O_2}} \right)$ is $ + 4$ and the oxidation state of lead in $\left( {PbS{O_4}} \right)$is$ + 2$. Hence, the oxidized species is lead and the species which is reduced is lead oxide. From the above reaction oxidizing agent is lead sulfate and the reducing agent is lead.