Pakistan MCQs

Oxygen contributes 16 of the 18 g/mol formula mass.
16/18×100 ≈ 88.9%.

The coefficients of H2 and H2O are equal.
Thus 4 mol H2 produce 4 mol H2O.

The mole ratio H2:NH3 is 3:2.
6 mol H2×2/3 = 4 mol NH3.

Percent yield is actual divided by theoretical times 100.
8/10×100 = 80%.

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.