1. Write and balance the chemical equation — ensure atom count is equal on both sides; check for polyatomic ions.
2. Convert all given quantities to moles — use n = mass / molar mass; or n = V / 22.4 (gas at STP); or n = N / Nₐ.
3. Identify the limiting reagent — divide moles of each reactant by its stoichiometric coefficient; the smallest value identifies the limiting reagent.
4. Use stoichiometric mole ratios — from the balanced equation, scale moles of limiting reagent to moles of desired product (or other reactant).
5. Convert moles of product to required units — mass (× molar mass), volume at STP (× 22.4 L), or number of particles (× Nₐ).
6. Check units at every step — dimensional analysis confirms the calculation path is correct.
7. Calculate excess reactant remaining (if asked) — moles of excess = initial moles − moles consumed by limiting reagent.
8. State the answer with correct significant figures and units.

Timeline — Discovery of Laws of Chemical Combination

1. 1789 — Lavoisier: Law of Conservation of Mass
2. 1799 — Proust: Law of Definite Proportions
3. 1803 — Dalton: Law of Multiple Proportions + Dalton's Atomic Theory
4. 1808 — Gay-Lussac: Law of Gaseous Volumes
5. 1811 — Avogadro: Avogadro's Hypothesis (equal volumes, equal molecules)
6. 1865 — Loschmidt: First estimate of Avogadro's number
7. 1909 — Perrin: Experimental confirmation of Nₐ via Brownian motion