Percent Composition and Empirical Formula
Percent Composition General Strategy Convert whole number ratio (moles) to mass percent Formula Mass Percent
Percent Composition Steps Multiply each whole number subscript by the appropriate molar mass. Divide the part of each molecule and divide by the total. Multiply by 100%.
Example 1 What is the percentage of each element in SO 2 ?
Example 2 What is the percentage of each element in Ca(OH) 2 ?
Empirical Formula General Strategy Convert mass percents to whole number ratio (moles) Mass Percent Formula
Empirical Formula Steps Assume each given percentage is a mass Divide each given percentage by the appropriate molar mass. Divide all values by the smallest number of moles to obtain a whole number ratio
Empirical Formula Definition: The formula with the simplest whole number ratio. Decimals you should not just round: 0.5 = ½ 0.25 = ¼ 0.33 = 1/ = 2/3
Molecular Formula Definition: A molecular formula may be simplified to an empirical formula.