Question

example 6 - 14: which one of the liquids, ho - ch₂ch₂ - oh or ch₃ch₂oh, has the highest vapour pressure at room temperature?

Explanation:

Step1: Analyze intermolecular forces

Vapour pressure is inversely related to the strength of intermolecular forces. Both liquids have hydrogen - bonding (due to - OH groups). But ethylene glycol (\(HO - CH_2CH_2 - OH\)) has two - OH groups, so it can form more hydrogen bonds. Ethanol (\(CH_3CH_2OH\)) has only one - OH group.

Step2: Relate intermolecular forces to vapour pressure

Stronger intermolecular forces (more hydrogen bonds in \(HO - CH_2CH_2 - OH\)) mean lower vapour pressure. Since \(CH_3CH_2OH\) has weaker intermolecular forces (fewer hydrogen bonds), it will have higher vapour pressure.

Answer:

\(CH_3CH_2OH\) has the highest vapour pressure at room temperature.