Pakistan MCQs

A p subshell contains three orbitals.
It can hold a maximum of six electrons.

Molarity equals moles divided by liters of solution.
0.50/2.0 = 0.25 M.

Mole ratios convert amounts of one substance into another.
They come directly from the balanced equation.

Chemical reactions rearrange atoms but do not create or destroy them.
Therefore total mass remains constant in a closed system.

A pure compound has constant composition.
This is also called the law of constant composition.

Percent composition is calculated from formula mass contributions.
The element percentages sum to approximately 100%.

Stoichiometry uses balanced equations to relate amounts.
It supports mass, mole, particle, and gas calculations.

Moles equal mass divided by molar mass.
18 g ÷ 18 g/mol = 1 mol.

Mass equals moles multiplied by molar mass.
2×58.5 = 117 g.

Particles equal moles times Avogadro's number.
0.5×6.022×10^23 = 3.011×10^23 molecules.

Moles equal particles divided by Avogadro's number.
1.2044×10^24 ÷ 6.022×10^23 = 2 mol.

Carbon contributes about 12 and two oxygens contribute 32.
The total molar mass is about 44 g/mol.