Presentation on theme: "Chapter 11 Empirical and Molecular Formulas"— Presentation transcript:
1Chapter 11 Empirical and Molecular Formulas ChemistryChapter 11Empirical and Molecular Formulas
2Empirical 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
3Empirical 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
7Molecular 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
8Molecular 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)
9ExampleA 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?