Question

Methane belongs to the homologous series of alkanes.
A ) True
B ) False

Answer 1

Hint: Homologous series contains compounds having similar chemical properties and same functional groups. Successive members of homologous series differ by a methylene group.

Complete step by step answer:
Organic compounds with the same general formula have carbon atoms of varying length. A series of compounds can be formed in which the general formula is the same and the individual members (organic compounds ) of the series differ by a repeating unit. Such a series is called a homologous series.

Alkanes form a homologous series. The general formula of alkanes is $${\text{C}}_n{\text{H}}_{2n+2}$$. Here, n represents the number of carbon atoms. In the homologous series of alkanes, the repeating unit is a methylene group. The methylene group is represented by the formula $$\text{C}{\text{H}}_2$$. Methane is the first member of alkane homologous series. The chemical formula of methane is $$\text{C}{\text{H}}_4$$. When n is 1, the chemical formula of methane is obtained.
$${\text{C}}_n{\text{H}}_{2n+2}={\text{C}}_1{\text{H}}_{2\left(1\right)+2}=\text{C}{\text{H}}_4$$
Ethane is the second member of the alkane homologous series. The chemical formula of ethane is $${\text{C}}_2{\text{H}}_6$$. When n is 2, the chemical formula of ethane is obtained.
$${\text{C}}_n{\text{H}}_{2n+2}={\text{C}}_2{\text{H}}_{2\left(2\right)+2}={\text{C}}_2{\text{H}}_6$$
Propane is the third member of the alkane homologous series. The chemical formula of propane is $${\text{C}}_3{\text{H}}_8$$. When n is 3, the chemical formula of propane is obtained.
$${\text{C}}_n{\text{H}}_{2n+2}={\text{C}}_3{\text{H}}_{2\left(3\right)+2}={\text{C}}_3{\text{H}}_8$$

The molecular formula of methane, ethane, propane, butane, pentane and hexane are shown below.
$$\text{C}{\text{H}}_4,{\text{C}}_2{\text{H}}_6,{\text{C}}_3{\text{H}}_8,{\text{C}}_4{\text{H}}_{10}\text{,}{\text{C}}_5{\text{H}}_{12}\text{,}{\text{C}}_6{\text{H}}_{14}$$

The structural formula of methane, ethane, propane, butane, pentane and hexane are shown below.
$$\begin{gathered} \text{C}{\text{H}}_4,\text{C}{\text{H}}_3\text{C}{\text{H}}_3,\text{ C}{\text{H}}_3\text{C}{\text{H}}_2\text{C}{\text{H}}_3,\text{ C}{\text{H}}_3\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_3\text{, } \\ \text{C}{\text{H}}_3\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_3\text{, C}{\text{H}}_3\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_2\text{C}{\text{H}}_3 \end{gathered}$$
From the above structural formulae, you can conclude that each successive member of the alkane homologous family has one additional methylene $$\left(\text{C}{\text{H}}_2\right)$$ group.

Methane belongs to the homologous series of alkanes.
Hence, the given statement is true

So, the correct answer is “Option A”.

Note: Alkenes form a homologous series. The general formula of alkenes is $${\text{C}}_n{\text{H}}_{2n}$$.
Alkynes form a homologous series. The general formula of alkynes is $${\text{C}}_n{\text{H}}_{2n-2}$$.