Concept: Vapour pressure is inversely proportional to the strength of intermolecular forces. Weaker intermolecular forces lead to higher vapour pressure because molecules can escape into the gaseous phase more easily.

Why (A) is correct:

The question compares the vapour pressure of two compounds. Let's assume compound (1) has stronger intermolecular forces than compound (2).

1. Compound (1) (e.g., a molecule with hydrogen bonding or strong dipole-dipole interactions) will have stronger intermolecular forces.

2. Compound (2) (e.g., a molecule with weaker London dispersion forces or less extensive dipole-dipole interactions) will have weaker intermolecular forces.

When intermolecular forces are weaker, less energy is required for molecules to escape from the liquid phase into the gaseous phase. This results in a higher concentration of molecules in the vapour phase above the liquid, leading to a higher vapour pressure.

Therefore, if compound (2) has weaker intermolecular forces than compound (1), its vapour pressure will be higher.

Option Analysis:

• A) Higher than that of (1): This is correct if compound (2) has weaker intermolecular forces than compound (1).
• B) Lower than that of (1): This would be true if compound (2) had stronger intermolecular forces than compound (1).
• C) Same as that of (1): This would only happen if both compounds had identical intermolecular forces and molecular weights, which is unlikely for two different compounds.
• D) Can be higher or lower depending upon the size of the vessel: Vapour pressure is an intensive property and does not depend on the size of the vessel, as long as there is enough liquid to establish equilibrium.

Correct Answer: (A)