The Mole Concept and Stoichiometry – O Level/IGCSE Chemistry Notes (Formulas & Solved Examples)
Your complete guide to mastering chemical calculations and the foundation of quantitative chemistry.
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Periodic Table Pillar (Chapter) | 2026/2027 Syllabus Guide (Notes) | Past Papers Solved (Notes) | Ultra Premium Study Notes (Crash Course)What is The Mole Concept? (The Chemist's Dozen)
The **Mole (mol)** is the SI unit for the amount of substance. It is simply a way to count the tiny, tiny particles (atoms, molecules, or ions) that make up matter. One mole contains **Avogadro's Constant ($N_A$)** particles:
$$ N_A = 6.02 \times 10^{23} \text{ particles} $$
Relative Masses ($A_r$ and $M_r$) and Molar Mass
These values are crucial for calculation. The **Molar Mass ($M$)** is the mass of one mole of a substance (g/mol).
👉 **Formula Sheet Link:** Master the base calculations. Learn the Moles Simple Method Here (Formula Sheet).
Stoichiometry: The Heart of Chemical Calculations
Stoichiometry uses the **mole ratios** from a **balanced chemical equation** to determine the amounts of reactants and products.
The Molar Volume of Gases (Volume $\leftrightarrow$ Moles)
At **Room Temperature and Pressure (R.T.P.)**, one mole of *any* gas occupies a volume of **$24 \text{ dm}^3$** (or $24,000 \text{ cm}^3$).
Concentration of Solutions (Molarity)
Concentration is often expressed in **moles per cubic decimeter ($\text{mol/dm}^3$)**.
Calculating Empirical and Molecular Formulae
This skill requires precision. The **Empirical Formula (E.F.)** is the simplest ratio, while the **Molecular Formula (M.F.)** is the actual ratio.
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Teacher Profile: Prof. Faisal Janjowa
**Watch Prof. Faisal Solve a Past Paper Mole Question:**
