Question

Assertion (A): Following are the members of a homologous series: ${\mathrm{CH}}_3\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{OH}$

Reason (R): A series of compounds with same functional group but differing by $–{\mathrm{CH}}_2–$ unit is called a homologous series.

• A. Both (A) and (R) are true and (R) is correct explanation of the assertion.
• B. Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Answer 1

The correct option is A

Both (A) and (R) are true and (R) is correct explanation of the assertion.

Explanation for Correct option:

Assertion:-

• ${\mathrm{CH}}_3\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{OH}$ this is a homologous series.
• They all have the same functional group that is $(-\mathrm{OH})$.
• They have similar chemical properties as well.
• But they differ from each other in successive addition of $–{\mathrm{CH}}_2–$units.
• Thus assertion is true.

Explanation for Reason:-

• A series of compounds that have the same functional group, but differ by $–{\mathrm{CH}}_2–$ unit is called a homologous series.
• They have the same chemical properties.
• Here in this series ${\mathrm{CH}}_3\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH},{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{OH}$ they have the same chemical properties and same functional group$(-\mathrm{OH})$.
• They just differ by $–{\mathrm{CH}}_2–$ unit.
• Thus the reason is also true and is the correct explanation for the assertion.

Therefore, option (A) Both (A) and (R) are true and (R) is correct explanation of the assertion is the correct answer