Presentation on theme: "Chapter 11 Empirical and Molecular Formulas"— Presentation transcript:
1 Chapter 11 Empirical and Molecular Formulas ChemistryChapter 11Empirical and Molecular Formulas
2 Empirical FormulasThe simplest whole number ratio of the elements in a compound (not necessarily the actual formula for a compound)ExH2O2 = HOH2O= H2OC6H12 = CH2C8H16 = CH2Can be calculated from % composition
3 Empirical Formula (Cheat Sheet) 1. % composition (if = 100%) converts tomassConvert from mass to molesCalculate simplest ratio(divide all # mol by the smallest # moles)3 ½. If not all whole numbers, multiply allby a whole # to create whole #’s4. Use simplest ratio as subscripts
7 Molecular Formula Actual number of moles of each element in a compound Need more info than just % compNeed molar mass of the empirical formulaNeed an experimental mass of the actual compound
8 Molecular Formula (Cheat Sheet) Use steps to calculate empirical formulaCalculate molar mass of empirical formulaThe question will give you experimental mass of the compoundExperimental massEmpirical form. Molar mass =5. Multiply subscripts in empirical by your answer (whole number)
9 ExampleA colorless liquid is found to be composed of 46.68% N and 53.32% O and has a molar mass of g/mol. What is the molecular formula?