Question

${{C}_{n}}{{H}_{2n+2}}$ is the general formula of a homologous series of hydrocarbons.
(i) Is this series saturated or unsaturated?
(ii) Name the series described above. Give the formula and name of the member with two carbon atoms.
(iii) Draw the structural formula of the first member of this series.
(iv) Define the homologous series and find the common difference between successive members of this family.
(v) Write the formula of n-butane and n-pentane.

Answer 1

Hint: All the organic compounds based on their structure and chemical properties have been divided into different families or groups. To study the properties of some organic compounds, these classifications of organic compounds will be useful. Generally, most organic compounds are poor electricity due to the covalent bond between carbon-carbon atoms.

Complete step by step answer:
A family or group of structurally similar organic compounds with the same functional group exhibits gradation in physical and chemical properties, and two adjacent members of which differ by $-C{{H}_{2}}$ group are known as Homologous series. The individual member of the series is called homologous and this phenomenon is named homology.
(i) The general formula of homologous series of hydrocarbons is ${{C}_{n}}{{H}_{2n+2}}$, where n is the number of carbon atoms in the series. This is the general formula of alkanes and these alkanes are saturated hydrocarbons. Hence, this homologous series is saturated.
(ii) the series named alkanes. The name of the first member with two carbon atoms is ethane and the formula is ${{C}_{2}}{{H}_{6}}({{C}_{2}}{{H}_{2X2+2}})$, where n=2.
(iii) methane is the first member of this series and structure shown below.

(iv) The homologous series of the same functional groups' substituents for hydrogen in a carbon chain and the common difference between a successive member of the family is $-C{{H}_{2}}$ group.
(v) n-butane molecular formula ${{C}_{4}}{{H}_{ 10}}$
$C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
n-pentane molecular formula ${{C}_{5}}{{H}_{12}}$
\[\] $C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$

Note: As the molecular mass increases in homologous series, physical properties gradation will be observed. Because increasing molecular mass then increasing boiling points and melting points in the series. But the chemical properties are defined by the functional group in this series.