Question

Define oxidising agent and reducing agent.

Answer 1

Oxidising agent - A substance that loses oxygen or electronegative radical or gains hydrogen or electropositive radical is called an oxidising agent.

• The element which undergoes reduction (gets reduced) is called the oxidising agent.

Example - When magnesium reacts with oxygen, O₂​ is reduced by losing oxygen atoms. Thus, O₂​ is an oxidising agent as it undergoes reduction.

$$\begin{gathered} 2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{MgO}\left(\mathrm{s}\right) \\ \mathrm{Magnesium}\mathrm{Oxygen}\mathrm{Magnesium}\mathrm{dioxide} \end{gathered}$$

Reducing agent - A substance that gains oxygen or electronegative radical or loses hydrogen or electropositive radical is called a reducing agent.

• The element which undergoes oxidation (gets oxidised) is called the reducing agent.

Example - Nitrogen is oxidised to nitrogen oxide (NO) by gaining an oxygen atom. Thus, NH_3​ is a reducing agent as it undergoes oxidation.

$$\begin{gathered} 4{\mathrm{NH}}_3\left(\mathrm{g}\right)+5{\mathrm{O}}_{2_{}}\left(\mathrm{g}\right)\to 4\mathrm{NO}\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ \mathrm{Ammonia}\mathrm{Oxygen}\mathrm{Nitrogen}\mathrm{oxide}\mathrm{water} \end{gathered}$$