Mass and moles conversions

The relationship between mass and amount in mol for any chemical substance is governed by its molar mass, which is defined as the mass of 1 mol of a pure substance expressed in grams.

Symbols and units

Oftentimes, the following notation is used:

mass [g]= m

amount [mol] = n

molar mass [g/mol] = M

Example 1

NaCl (table salt) has a molar mass of 58.44 g/mol

What is the mass of 2.10 mol ?

m(NaCl) = n(NaCl) * M(NaCl) = 2.10 mol * 58.44 g/mol = 122.7 g/mol

Example 2

H₂O (water) has a molar mass of 18.02 g/mol . What is the amount of water (in mol) equivalent to 4.3 g ?

n(H₂O) = m(H₂O) / M(H₂O)= 4.3 g / 18.02 (g/mol)= 0.239 mol.