What is a mole?

A mole is a unit of measurement for the amount of a substance. One mole is 6.02 x 10^23 particles in a substance, known as Avogadro's constant. This is because this is the number of atoms in  12g of Carbon- 12(the relative atomic mass of the carbon atoms). The molar mass is always equal to the atomic mass of an atom, for example 1 mole of oxygen is equal to 16 grams.