Question

Assertion
Ethylene glycol is a dihydric alcohol.
Reason
The general formula for a dihydric alcohol is ${C_n}{H_{2n}}{(OH)_2}$
A. Both assertion and reason are correct and reason is the correct explanation of assertion.
B. Both assertion and reason are correct but reason in not the correct explanation of assertion.
C. Assertion is correct but reason is incorrect.
D. Assertion is incorrect but reason is correct.

Answer 1

In ethylene glycol two hydroxyl groups are attached to the carbon atom present adjacent to each other. The molecular formula of ethylene glycol is ${C_2}{H_6}{O_2}$. The value of n is 2.

Complete answer: Dihydric alcohols are classified as any group of alcohol which contains two hydroxyl groups attached to the two molecules by a sigma bond. Example of dihydric alcohol is catechol which contains two hydroxyl groups attached to the two carbon atoms of the benzene ring. The other important example of dihydric alcohol is ethylene glycol. It is a vicinal diol which means that the two hydroxyl groups are attached to the carbon atom adjacent to each other. The IUPAC name of ethylene glycol is Ethane-1,2-diol. As ethylene glycol has extensive H-Bonding, it is viscous in nature and generally has a higher boiling point than other alcohols.
The general formula of dihydric alcohol is ${C_n}{H_{2n}}{(OH)_2}$
The molecular formula of ethylene glycol is ${C_2}{H_6}{O_2}$. It contains two carbon atoms, six hydrogen atoms and two oxygen atoms.
The value of n is 2.
The formula of ethylene glycol is ${C_n}{H_{2n}}{(OH)_2}$= ${C_2}{H_{2(2)}}{(OH)_2} = {C_2}{H_4}{(OH)_2}$
Thus, both assertion and reason are correct and the reason is the correct explanation for the assertion.
Therefore, the correct option is A.

Note: Ethylene glycol is prepared from ethylene by reacting with potassium permanganate in an alkaline medium. The reagent potassium permanganate is an oxidizing agent.