Pakistan MCQs

Effusion rates depend on molar mass.
Lighter gases generally effuse faster.

Sublimation bypasses the liquid phase.
Dry ice changing to carbon dioxide gas is an example.

Each carbon has three sigma-bonding regions.
The remaining p orbitals form the pi bond.

Deposition is the reverse of sublimation.
Frost formation is a familiar example.

Each carbon has two electron domains.
Sp hybridization gives linear geometry and leaves two p orbitals for pi bonds.

At equilibrium, evaporation and condensation rates are equal.
Vapor pressure increases with temperature.

Sigma bonds have electron density along the internuclear axis.
Every single covalent bond is a sigma bond.

Bubbles can form throughout the liquid at the boiling point.
Lower external pressure lowers boiling temperature.

Pi bonds place electron density above and below the bond axis.
Double and triple bonds contain pi bonding.

Evaporation can occur below the boiling point.
Higher-energy surface molecules escape preferentially.

The first bond between two atoms is sigma.
The second bond is pi.

Cohesive forces pull surface molecules inward.
Stronger intermolecular forces generally increase surface tension.