Pakistan MCQs

The balanced equation fixes the required mole ratio.
Comparison of available amounts shows that O₂ is consumed first.

The coefficients of CaCO₃ and CO₂ are both one.
Two moles of CaCO₃ therefore form two moles of CO₂.

The balanced equation fixes the required mole ratio.
Comparison of available amounts shows that Na is consumed first.

Percentage yield = actual yield ÷ theoretical yield × 100.
(8 ÷ 10) × 100 = 80%.

Percentage yield = actual yield ÷ theoretical yield × 100.
(36 ÷ 40) × 100 = 90%.

Percentage yield = actual yield ÷ theoretical yield × 100.
(72 ÷ 80) × 100 = 90%.

Complete combustion gives carbon dioxide and water.
Limited oxygen may produce carbon monoxide or soot.

Moles = mass ÷ molar mass = 64 ÷ 32.
The sample therefore contains 2 mol.

Hydrogenation converts an unsaturated bond toward saturation.
A metal catalyst is commonly used.

Moles = mass ÷ molar mass = 50 ÷ 100.
The sample therefore contains 0.5 mol.

Esterification is a condensation reaction.
An acid catalyst is often used.

Moles = mass ÷ molar mass = 200 ÷ 100.
The sample therefore contains 2 mol.