1. Moles and Avogadro’s Number Molar mass, Molecular weight

2. Mole (mol) is a unit of measurement used to express amounts of a chemical substance. 1 mol is defined as the mass of a substance, expressed in grams, equal to the substance's mean molecular mass. For example, the mean molecular mass of water is 18.015, so one mole of water is equal to 18.015 grams of water.

3. Avogadro’s Number (constant) is defined as the number of atoms or molecules in one mole of a given substance. The number is 6.02214 X 10 23 and is expressed in units/mol (atoms/mol or molecules/mol).