Moles

In chemistry we measure quantities in many ways. We measure mass in Kg, volume in litres or cm3, for chemical quantities we also use the mole. A mole represents a number of particles. This is a very large number. This number is 6.02E23, and known as Avogadro's number. So a mole in chemistry represents Avogadro's number particles of any given substance.

The mole is one of the seven SI units, and it is represented by the symbol 'n' when used in a mathematical formula. We understand that matter is made of different kinds of particles, so the term representative particles refers to either atoms, ions or molecules.

Molecular mass

Mole = Mass/Molecular Mass

Measured in g/Mol
E.g. H2O 1+1+16 = 18g/Mol

Volume of a Mole of gas

Mole = Particles/Avogadro's number

The volume of a mole of gas is more predictable than the volume of a mole of a liquid or a solid. The volume of a mole of gas is usually measured at Standard Temperature & Pressure (STP).
Standard temperature is: 0° (273K) and
Standard pressure is: 1 Atmosphere (atm), 760mmHg or 103.8Kpa
At STP, one mole of a gas occupies a volume of 22.4 litres. This quantity of 22.4 litres is also know as the molar volume of gas.

Mole = Volume (litres)/22.4 litres