ECAT MCQs

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.

A triple bond contains one axial sigma bond.
Two perpendicular pi bonds complete the bond order of three.

Viscosity arises from internal friction.
It usually decreases for liquids as temperature increases.

Hydrogen bonding is stronger than ordinary dipole forces.
It strongly affects boiling point and solubility.

Dispersion forces occur in all atoms and molecules.
Their strength generally increases with polarizability.

Polar molecules align partially positive and negative regions.
These attractions affect physical properties.