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Chem3 Ch5.p2.

Percent Composition

Percent Composition:ProcessAnswer
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%
Created by: nikkimem32