ICSE Class 10 Chemistry: Mole Concept — Complete Notes 2026

The Mole — Definition and Significance

• 1 mole = 6.022 × 10²³ particles (Avogadro's number N_A)
• Molar mass = mass of 1 mole of substance in grams (numerically equal to relative molecular mass)
• Mole bridges atomic-scale chemistry with measurable laboratory quantities

Molar Volume of Gases

• At STP (0°C, 1 atm): 1 mole of any gas occupies 22.4 L
• At RTP (25°C, 1 atm): 1 mole occupies ~24 L
• Application: convert volume of gas at STP to moles: n = V/22.4

Percentage Composition

• % element = (mass of element in formula / molar mass) × 100
• Example: % C in CO₂ = (12/44) × 100 = 27.3%
• Used to verify formula and check purity of compound

Empirical and Molecular Formula

• Empirical formula: simplest whole-number ratio of atoms
• Molecular formula = n × empirical formula; n = Mr/empirical formula mass
• Step-by-step: % → moles → divide by smallest → whole number ratio

Stoichiometry and Mole Ratios

• Balanced equation gives mole ratio of reactants and products
• Mole-to-mole: N₂ + 3H₂ → 2NH₃; 1:3:2 mole ratio
• Mole-to-mass and mass-to-mass conversions using molar masses

Limiting Reagent and Percentage Yield

• Limiting reagent is fully consumed first; determines maximum product
• Find moles of each reactant, divide by stoichiometric coefficient — smallest is limiting
• % yield = (actual yield / theoretical yield) × 100%

Numericals — Mole Concept

• Find moles and molecules in 36 g of water
• Calculate mass of NaCl produced from 5 g of Na with excess Cl₂
• Determine empirical formula given: C=40%, H=6.67%, O=53.33%