ECAT Chemistry MCQs

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.

Hydrogen bonds require significant energy to overcome.
This raises water's boiling point relative to similar-size molecules.

Each C=O bond is polar, but the molecule is linear and symmetric.
The bond dipoles cancel.

Water has polar O-H bonds and a bent shape.
The bond dipoles do not cancel.

Solid particles occupy fixed average positions.
They still vibrate about those positions.

Carbon has two electron domains from the two double bonds.
They arrange 180 degrees apart.

A liquid takes the shape of its container.
Its particles remain close but can flow past one another.

Boron has three bonding regions and no lone pairs.
The molecule is planar with approximately 120-degree angles.

A gas expands to fill its container.
Its particles are widely separated and move rapidly.

The octet rule is a useful main-group bonding guideline.
Hydrogen, boron, and expanded-valence species are exceptions.