Question

A substitution reaction of methane is-
A. $C{H_4} + C{l_2} \to CC{l_4} + HCl$
B. $C{H_4} + C{l_2} \to CHC{l_3} + HCl$
C. $C{H_4} + C{l_2} \to C{H_3}Cl + HCl$
D. $C{H_4} + C{l_2} \to C{H_2}C{l_2} + HCl$

Answer 1

Substitution reaction is a reaction in which one atom of a molecule is replaced with an atom of another molecule. When methane reacts with chlorine in presence of diffused sunlight to produce compounds containing chlorine then this reaction is called chlorination of methane.

Step-by-step solution-
Methane is a colourless and odourless gas. It is also known as marsh gas. It is produced during coal and natural gas production. It is one of the greenhouse gases and it is toxic in nature.
Methane reacts with chlorine in presence of ultraviolet light or by heating it to a temperature between $523 - 773{\text{K}}$ to produce chloromethane and hydrogen chloride. The reaction is given as-
$C{H_4} + C{l_2}\xrightarrow{{{\text{uv light}}}}C{H_3}Cl + HCl$
This reaction is a substitution reaction because one atom of hydrogen is replaced by one atom of chlorine to form methyl chloride. It is also known as chloromethane. Its properties are-
- It is a clear, colorless gas with mild odor.
- It is toxic and extremely flammable.
- It is heavier than air.
- It is soluble in water
In excess of chlorine, the reaction proceeds further and all the four hydrogen atom are replaced by four atoms of chlorine to form carbon tetrachloride $CC{l_4}$ .The reaction is given as-
$C{H_3}Cl + C{l_2}\xrightarrow{{{\text{uv light}}}}C{H_2}C{l_2} + C{l_2} \to CHC{l_3} + C{l_2} \to CC{l_4}$

Hence the correct answer is C.

Note: The uses of methane are-
- It is used in gas-fired power stations and in generation of electricity.
- It is used as a fuel in rockets, automobiles and water heaters.
- It is also used as an antifreeze ingredient.
- It is also used for sanitization of products.