Question

Which of the following is an electrolytic decomposition reaction?
\[\begin{align}
  & \text{A}\text{. 2HgO}\xrightarrow{\text{heat}}\text{2Hg+}{{\text{O}}_{\text{2}}} \\
 & \text{B}\text{. CaC}{{\text{O}}_{\text{3}}}\xrightarrow{\text{heat}}\text{CaO+C}{{\text{O}}_{\text{2}}} \\
 & \text{C}\text{. 2}{{\text{H}}_{\text{2}}}\text{O}\xrightarrow{\text{electrolysis}}\text{2}{{\text{H}}_{\text{2}}}\text{+}{{\text{O}}_{\text{2}}} \\
 & \text{D}\text{. }{{\text{N}}_{\text{2}}}\text{+3}{{\text{H}}_{\text{2}}}\to \text{2N}{{\text{H}}_{\text{3}}} \\
\end{align}\]

Answer 1

Hint:An electrolytic decomposition reaction can be identified by a reaction in which a single compound is broken into two or more products by the application of electricity. The process of electrolysis occurs in this reaction.

Complete answer:
The above question belongs to the concept of chemical reaction and its types. A chemical reaction is a phenomenon that involves rearrangement of the molecular or the ionic structure of a compound, molecule or a substance. In a chemical reaction one or more reactants combine together to form a product. It is an irreversible process as the whole structure of the molecule or compound is changed. Chemical reactions are of many types. The type of chemical reaction in the above question is electrolytic decomposition reaction. This reaction is also of two types. In this reaction simultaneously two processes are occurring, one is decomposition and the other is electrolysis. In electrolytic decomposition reaction, the decomposition or the breaking of compound occurs due to electrolysis. Electrolysis is the breaking or decomposition of a compound by passing electric current.
Now, in the first and second reaction the decomposition of the compound is occurring but the decomposition is due heat. In the fourth reaction the compound is formed. In case of third reaction the decomposition of the compound is because of electrolysis. The water breaks into hydrogen and oxygen when electric current is passed. This reaction is also called electrolysis of water. Thus, in this reaction the decomposition of the compound is taking place due to electricity.

So, option C is the correct answer.

Note:
The electrolytic decomposition of water takes place in an electrolyser. This decomposition has a standard potential of $ - 1.23$ V. Electrolysis is used in the real world for the production of many metals such as aluminium, magnesium, chlorine and many others.