Benzoic acid is almost insoluble in which of the following solvents?

Cold water

The correct answer is option 3. Cold water.

Benzoic acid is a polar molecule due to the presence of the carboxyl group \((–COOH)\), which contains an oxygen atom with two lone pairs of electrons. This polarity makes it soluble in polar solvents like water. However, the solubility of benzoic acid in water is limited, especially at low temperatures, because it is only sparingly soluble in cold water. As the temperature increases, the solubility of benzoic acid in water also increases due to the higher kinetic energy of the water molecules, which facilitates the dissolution process.

On the other hand, benzoic acid is nearly insoluble in non-polar solvents such as ether and benzene. This is because non-polar solvents lack the ability to effectively interact with the polar carboxyl group of benzoic acid through hydrogen bonding or dipole-dipole interactions. As a result, the intermolecular forces between benzoic acid molecules are stronger than the interactions between benzoic acid and non-polar solvents, leading to poor solubility.

In summary:

Benzoic acid is sparingly soluble in cold water but dissolves readily in hot water due to its polar nature and the ability to form hydrogen bonds with water molecules.

Benzoic acid is nearly insoluble in non-polar solvents like ether and benzene due to the lack of effective interactions between the polar carboxyl group and non-polar solvent molecules.

Therefore, the correct answer is Cold water