ECAT MCQs

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.

Oxygen has two bonding pairs and two lone pairs.
Lone-pair repulsion produces a bent molecule.

After formation, a coordinate bond behaves like an ordinary covalent bond.
The electron-pair donor provides both bonding electrons.

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

Lewis structures use lines and dots for bonds and lone pairs.
They help predict connectivity and formal charge.

Lone pairs influence shape and reactivity.
They repel bonding pairs strongly in VSEPR theory.

A single bond has order one, double bond two, and triple bond three.
Higher bond order generally means shorter, stronger bonds.

Triple bonds have higher bond order than single or double bonds.
They are usually shorter and stronger.

No single resonance structure fully represents the electron distribution.
The real structure is a resonance hybrid.

Formal charge helps compare possible Lewis structures.
Preferred structures often minimize charge separation.