# Percentage Composition

## Presentation on theme: "Percentage Composition"— Presentation transcript:

Percentage Composition

Percent Part X 100% Whole Percent by mass = Mass of element X 100%
Mass of compound

Percent Composition Can be determined by analysis.
Or, if you know the formula: Just assume you have 1 mole Divide the mass of each element by the formula mass of the compound

Percent Composition of H2O
2 X H = 2 X 1.0 = 2.0 1 X O = 1 X 16.0 = 16.0 Molar mass = = 18.0 %H = (2.0/18.0) X 100% = 11.2% %O = (16.0/18.0) X 100% = 88.8%

Percent Composition of C6H12O6
6 X C = 6 X 12.0 = 72.0 12 X H = 12 X 1.0 = 12.0 6 X O = 6 X 16.0 = 96.0 Molar mass = grams % C = % H = % O = (72.0/180.0) X 100% = 40.0% (12.0/180.0) X 100% = 6.67% (96.0/180.0) X 100% = 53.3%

Percent Composition of NaCl
Molar mass of NaCl = 58.5 g/mole % Na = 23.0/58.5 X 100% = 39.3% % Cl = 35.5/58.5 X 100% = 60.7% (Or, 100% % = 60.7%)

Percentage Composition
They won’t remind you that you have to calculate the formula mass!