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]= in grams equals m
amount [mol] = in moles equals n
molar mass [g/mol] = M is grams per moles equals capital M
Example 1
NaCl (table salt) has a molar mass of 58.44 g/mol sodium chloride (table salt) has a molar mass of 58.44 grams per mole
What is the mass of 2.10 mol moles ?
m(NaCl) = n(NaCl) * M(NaCl) = 2.10 mol * 58.44 g/mol = 122.7 g/mol m(NaCl) equals n(NaCl) times M(NaCl) equals 2.10 moles times 58.44 grams per moles equals 122.7 grams per mole.
Example 2
H2O (water) has a molar mass of 18.02 g/mol grams per mole . What is the amount of water (in mol) equivalent to 4.3 g grams ?
n(H2O) = m(H2O) / M(H2O)= 4.3 g / 18.02 (g/mol)= number of moles of water equals moles divided by Molar mass equals 4.3 grams divided by 18.02 grams per mole equals 0.239 mol.