Calculations for Amount of Substance: Module 2: Foundations In Chemistry: Chemistry OCR A A Level

Relative Atomic Mass

The mass of an atom compared to carbon-12 on a scale where carbon is exactly 12.

Relative Isotopic Mass

The mass of an isotope compared to carbon-12 on a scale where carbon is exactly 12.

Isotope

An atom of an element with different number of neutrons.

Mole

A mole is a measure of the amount of any substance. It contains the same number of particles, equal to the number of carbon-12 atoms in exactly 12 g of the isotope.

Empirical Formula

The empirical formula of a substance is the simplest whole number ratio of atoms of each element present.

Avogadro’s Constant

The Avogadro constant , NA, is the number of atoms per mole of the carbon-12 isotope (6.02 x 10^23 mol^−1 ).

Water of Crystallisation

Water molecules form an essential part of the crystal structure of some compounds, known as water of crystallisation.

Molar gas volume

Molar gas volume is the volume per mole of a gas. The units of molar volume are dm^3 mol^-1. At room temperature and pressure, the molar volume is 24 dm^3 mol^-1.