What is a homologous series ? Explain with an example.

Explanation

As series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series .In this series carbon atoms can be linked together to form chains of varying lengths.In addition ,hydrogen atom or atoms on these carbon chanins can be replaced by any of the functional groups .The presence of a functional group such as alcohol dictates the properties of the carbon compound regardless of the length of the carbon chani.
For example : methane ,ethane ,propane ,butane etc .are all part of the alkane homologous series .The general formula of this series is `C_(n)H_(2n+2)`.
Methane `-CH_(4)`
Ethane - `CH_(3)CH_(3)`
Propane `-CH_(3)CH_(2)CH_(3)`
Butane - `CH_(3)CH_(2)CH_(2)CH_(3)`
It can be observed that there is a difference of `-CH_(2)` unit between each successive compound . As the molecular mass increases in any homologous series ,the melting points and boiling points also increases. Other physical properties such as solubility in a particular solvent also show a similar gradation .But the chemical properties ,which are determined by the funtional group ,remain similar in a homologous series.