Question

Explain the following in terms of gain or loss of oxygen with two examples each
(A) Oxidation
(B) Reduction

Answer 1

Hint: Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. Oxidation occurs when the oxidation state of a molecule, atom or ion is increased. The opposite process is called reduction, which occurs when there is a gain of electrons or the oxidation state of an atom, molecule, or ion decreases.

Complete step by step solution:
When during a chemical reaction, oxygen is added to some element or compound and hydrogen is eliminated, the compound is known to be oxidized and the reaction is known as oxidation reaction.The example of oxidation reaction is as follows:
\[2S\left( s \right)\text{ }+\text{ }{{O}_{2}}~\left( g \right)\text{ }\to \text{ }S{{O}_{2}}~\left( g \right)\]
\[C{{H}_{4}}~\left( g \right)\text{ }+\text{ }2{{O}_{2}}~\left( g \right)\text{ }\to \text{ }C{{O}_{2}}~\left( g \right)\text{ }+\text{ }2{{H}_{2}}O\text{ }\left( l \right)\]
In the first reaction, sulphur is oxidized to sulphur dioxide, by addition of oxygen, and in the second reaction, methane is oxidized to carbon dioxide. In both the reactions, oxygen gas acts as an oxidizing agent.
When during a chemical reaction, oxygen is removed from some element or compound and hydrogen is added, the compound is known to be reduced and the reaction is known as reduction reaction. Below are some examples of reduction reactions:
\[CuO+{{H}_{2}}\xrightarrow{\Delta }Cu+{{H}_{2}}O\]
\[ZnO+{{H}_{2}}\xrightarrow{\Delta }Zn+{{H}_{2}}O\]
In the first reaction, Copper oxide is reduced to copper metal on reaction with hydrogen gas, oxygen is removed from copper. Similarly in the second reaction, zinc oxide is reduced to Zinc metal, by reaction with hydrogen gas and removal of oxygen atom. Here, hydrogen gas acts as a reducing agent.

Note: An oxidizing agent is a reactant that removes electrons from other reactants during a redox reaction. The oxidizing agent typically takes these electrons for itself, thus gaining electrons and being reduced. An oxidizing agent is thus an electron acceptor. Reducing agent is 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 the redox reaction.