Converting grams to moles
The number of moles in a sample is found by dividing the mass by the molar mass (molecular weight):
n = m / M
Where n = moles, m = mass (g), and M = molar mass (g/mol).
Example: 36 g of water (M = 18.015 g/mol): n = 36 / 18.015 = 1.999 mol