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, percent).
