Percentage Composition --Nov.29

Definition: Percentage by mass of “species” in a chemical formula.

Ex. What is the percentage composition of CO₂?

 *assume you have 1 mole

Total MM=44.0g/mol

Percentage of C=(12g/mol)/(44g/mol)×100% = 27.3%

Percentage of O=(16g/mol×2)/(44g/mol)×100% = 72.7%

*(27.3%+72.3%=100%)

Percentage composition tells you which elements are in the compound and how much of each there is.

Fomula(useless):

                                              Mass of element

Percentage composition=—————————— ×100%

                                             Mass of compound