Chapter 1
Matter, Atoms & Mole Concept
The Mole Concept Formulas
SI: molNumber of Moles (n) = Given Mass (m) / Molar Mass (M) = Number of Particles (N) / N_A
One mole of any substance contains exactly 6.022 × 10²³ elementary entities (atoms, molecules, or ions).
Variables: N_A = Avogadro Constant = 6.022 × 10²³ particles/mol
Exam Tip: At standard STP, 1 mole of any ideal gas occupies 22.4 Liters of volume.
Mass Percentage of Element in Compound
Mass % = (Total Mass of Element in 1 mol of Compound / Molar Mass of Compound) × 100%
Derived directly from Proust Law of Definite Proportions.
Variables: e.g. In H2O: H % = (2 × 1.008 / 18.016) × 100% ≈ 11.2%, O % ≈ 88.8%
Exam Tip: Verify that the sum of mass percentages of all constituent elements equals 100%.