Question

If octane and propane are members of a homologous series, then these two compounds differ by ________.

• A. ${\text{C}}_5{\text{H}}_{10}$
• B. ${\text{C}}_4{\text{H}}_8$
• C. ${\text{C}}_4{\text{H}}_4$
• D. ${\text{C}}_2{\text{H}}_2$

Answer 1

The correct option is A ${\text{C}}_5{\text{H}}_{10}$

$\bullet$ Octane and propane belong to the same homologous series.

$\bullet$ 'Oct' represents 8 carbon atoms and 'prop' represents 3 carbon atoms.

$\bullet$ Since successive members of a homologous series differ by a ${\text{CH}}_2$ group, octane and propane differ by $8-3=5{\text{CH}}_2$ groups.

Thus, octane and propane differ by ${\text{C}}_5{\text{H}}_{10}$.