Pakistan MCQs

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

Atomic number identifies the element.
In a neutral atom it also equals the number of electrons.

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.

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.

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

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

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

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

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