NAT MCQs

Percent yield measures reaction and recovery efficiency.
Values below 100% commonly result from losses or incomplete reaction.

Heterogeneous mixtures contain distinguishable regions or phases.
Examples include sand in water and granite.

Molarity is a common concentration unit.
Its value changes with temperature because solution volume can change.

A physical change alters form or state without changing chemical identity.
Ice and liquid water are both H2O.

Molality is based on solvent mass.
It is largely independent of temperature.

Rusting forms new iron oxide substances.
Chemical changes involve rearrangement of atoms and new products.

Mass percent expresses composition on a mass basis.
All component mass percentages sum to 100%.

Density describes how much mass is packed into a volume.
It is commonly expressed in g/cm³ or kg/m³.

The mole is the SI base unit for amount of substance.
One mole contains Avogadro's number of specified entities.

Avogadro's constant gives the number of entities in one mole.
The entities may be atoms, molecules, ions, or formula units.

Molar mass is numerically related to relative atomic or molecular mass.
Its common unit is g/mol.

An empirical formula shows the lowest integer ratio of elements.
It may differ from the molecular formula.