Don’t forget to
multiply mass
by #of Moles
Percentage Composition
% Composition is the % by mass of each element in a
compound.
Ex: Find the percentage composition of sodium in sodium
chloride:
Na+ Cl - : formula is NaCl
1 mol Na x 22.99 g Na = 22.99 g Na
1 mol Na
1 mol Cl x 35.45 g Cl = 35.45 g Cl
1 mol Cl
molar mass NaCl = 58.44 g/mol
22.99 g Na x 100 = 39.34 % Na
58.44 g NaCl
Find the percentage composition of sodium nitrate.
Na+ NO3 - : formula is NaNO3
1 mol Na x 22.99 g Na = 22.99 g Na
1 mol Na
1 mol N x 14.01 g N = 14.01 g N
1 mol N
3 mol O x 16.00 g O = 48.00 g O
1 mol O molar mass NaNO3 = 85.00 g/mol
