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Chem3 Ch5.p2.
Percent Composition
Percent Composition:Process | Answer |
---|---|
percent composition | mass percent of each element in a compound |
Percent Composition Formula | % element = g element/g compound X 100% |
Two ways to compute % composition: | 1. Experitmental masses of element in the compound. 2. Chemical formula, using mole ratios |
Mass Percent from formula:Step 1 | Convert moles of compound to grams using the molar mass |
Mass Percent from formula:Step 2 | Write a subscript X from the formula as (X mol element/ 1 mol compound) |
Mass Percent from formula:Step 3 | Multiply by 100% |
Percent Composition of iron (III) oxide, Fe2O3:Step1a & b &c | 1a. 2 mol Fe (55.85 g/mol) = 111.70g 2b. 3 mol O (16.00 g/mol) =48.00g 1c. 111.70g + 48.00g = 159.70g |
Percent Composition of iron (III) oxide, Fe2O3:Step 2a & b | % Fe = 111.70g/159.70g X 100% = 69.944% 2b. % O = 48.00g/159.70g X 100% = 30.06% |