Helpful hints to solve molecular formula, empirical formula, and percent composition problems.

Empirical Formulas 1. Change % to grams if necessary 2.Divide each gram amount by their respective molar masses 3.Divide all mole amounts by the smallest mole amount 4.Multiply to get whole numbers if necessary 5.Use the whole numbers you found in step 3 or 4 as the subscripts for your formula.

Molecular Formula 1.Find the empirical formula if needed 2.Find the empirical formula mass 3.The molecular mass will be given to you … divide it by the empirical mass 4.Use the number you get in step 3 to multiply the subscripts in the empirical formula to get the molecular formula

% Composition 1.Find the mass of the entire substance 2.Divide each part by the whole mass and multiply by The sum of your percents should equal 100