Percent Composition. Can be calculated if given: masses of elements in compound OR the chemical formula. Percent Composition. Can be used to: calculate the mass of elements in a compound determine the empirical formula of a compound determine the molecular formula of a compound.
masses of elements in compound
the chemical formula
calculate the mass of elements in a compound
determine the empirical formula of a compound
determine the molecular formula of a compound
25.9% N = 25.9g
74.1% O = 74.1g
1.85 : 4.63 = 1 : 2.5
(If the result is not within 0.1 of a whole number, multiply all numbers by a whole number)
2 ( 1 : 2.5) = 2 : 5
Given the empirical formula and the gram formula mass (gfm)
Given the percent composition and the gram formula mass (gfm)
Calculate the molecular formula for NaO having a gfm of 78g.
Determine the efm (empirical formula mass).
NaO = 23.0g + 16.0g = 39.0
78.0 = 2
Find the molecular formula for a compound having a composition of 58.8% C, 9.8% H and 31.4% O and a gmm of 102g/mol.
C = 102g/mol x 58.8% = 60.0g/mol
H = 102g/mol x 9.8% = 10.0g/mol
O = 102g/mol x 31.4% = 32.0g/mol
C = 60.0g/mol = 5
H = 10.0g/mol = 10 1.0g
O = 32.0g/mol = 2
number of moles by the smallest number of moles. Use moles as subscripts for components of compound