Question

The solubility of alcohols in water gradually increases with molecular weight.
A.True
B.False

Answer 1

We can define alcohols as organic compounds that contain a hydroxyl group that is covalently bonded to a carbon atom. The general formula of alcohol is ${\text{R - OH}}$. R is the alkyl group. We can classify alcohols into three types as primary, secondary and tertiary alcohols.

Complete step by step answer:
We know that alcohol is soluble in water. This is because the hydroxyl group in the alcohol has the ability to form hydrogen bonds with water molecules.
Alcohols that contain smaller hydrocarbon chains are highly soluble in water.
As the hydrocarbon chain length increases, the solubility in water decreases.
The hydrocarbon chain with four and higher carbon atoms, shows decrease in solubility and becomes visible as the mixture forms two immiscible layers of liquid.
The reason why the solubility decreases as the length of the hydrocarbon chain increases is because it needs more energy to overcome the hydrogen bonds between the alcohol molecules as the molecules are closely packed together as the size and mass increases.

Therefore, the correct option is (B).

Note:
As we know alcohols have strong intermolecular hydrogen bonding. The ${\text{OH}}$ group present in the alcohol allows the molecules to participate in hydrogen bonding. A larger amount of energy is required to break the intermolecular hydrogen bonding in alcohols hence, they have higher boiling and higher melting points compared to amines of comparable molar mass. The oxidation of a primary alcohol forms an aldehyde and the oxidation of secondary alcohol yields a ketone. Tertiary alcohols do not undergo oxidation under the conditions normally used.