To determine percent composition:
Determine the amu of each element in the compound (periodic table).
Multiply the amu by the element's subscript in the formula to determine the mass of the element in that compound.
Determine the molar mass of the compound (sum the masses of each element).
Divide each element's mass by the compound's molar mass, then multiply by 100.
Rounding - generally, round the percent composition to the nearest hundredth.
Directions - determine the percent composition of each element in the following compounds. Do not forget to include the correct unit for each calculation (grams - g, percent - %)
Na3PO4
Molar Mass of compound =
Percent Compositions:
Na =
P =
O =
Do not forget to include the correct unit for each calculation (grams - g, percent - %)
H2O2
Molar mass =
Percent Compositions:
H =
O =
Do not forget to include the correct unit for each calculation (grams - g, percent - %)
CO2
Molar Mass of Compound =
Percent Compositions:
C =
O =
C6H12O6
Molar Mass of Compound =
Percent Compositions:
C =
H =
O =
(NH4)2SO4
Molar Mass of Compound =
Percent Compositions:
N =
H =
S =
O =
NaClO
Molar Mass of Compound =
Percent Compositions:
Na =
Cl =
O =
MgSO4
Molar Mass of compound =
Percent Compositions:
Mg -
S =
O =
(NH2)2CO
Molar Mass of Compound =
Percent Compositions:
N =
H =
C =
O =
C10H14N2
Molar Mass of Compound =
Percent Compositions:
C =
H =
N =
CaSO4 . 2 H2O (hydrated compound)
Molar Mass of Compound =
Percent Compositions:
Ca =
S =
O =
H =