Easy Practice — Set 2

Quick Recap — Percentage Composition & Formulae

• Mass % of an element $=\dfrac{\text{mass of element in 1 mol}}{\text{molar mass}}\times100$.
• Empirical formula: simplest whole-number ratio of atoms; molecular formula $=(\text{empirical})_n$.
• Vapour density: $M=2\times VD$.
• At STP: $V=n\times22.4$ L; moles of atoms in a molecule = (atoms per molecule) $\times$ moles.