Unit V: The Mole Concept V.5. Empirical and Molecular Formulae

Empirical Formula  Simplest Formula  Gives the simplest whole number ratio of elements in a compound

Molecular Formula  Gives the ACTUAL number of each kind of atom in a molecule and compound

Molecular vs. Empirical

Molecular FormulaEmpirical Formula P 4 O 10 C 10 H 22 C 6 H 18 O 3 C 5 H 12 O N2O4N2O4

Molecular vs. Empirical Molecular FormulaEmpirical Formula P 4 O 10 P2O5P2O5 C 10 H 22 C 5 H 11 C 6 H 18 O 3 C2H6OC2H6O C 5 H 12 O N2O4N2O4 NO 2

Finding Empirical Formulas A sample of an unknown compound is analyzed and found to contain 8.4 g of “C” 2.1 g of “H” and 5.6 g of “O”. Find the empirical formula.

Finding Empirical Formulas Element Mass (g) Atomic Mass Moles Sm.Moles Smallest Ratio C H O

Finding Empirical Formulas grams of a compound made up of carbon, hydrogen and oxygen are found to contain g of carbon and g of hydrogen. a) Find the mass of oxygen b) Find the empirical formula

Finding Empirical Formulas Element Mass (g) Atomic Mass Moles Sm.Moles Smallest Ratio C H O

Finding Empirical Formulas A while powder used in paints has the following composition:  Ba69.58%  C6.090%  O24.32% Find the Empirical Formula

Finding Empirical Formulas Element Mass(g)Atomic Mass Moles Sm.Moles Smallest Ratio Ba C O

WHAT HAPPENS WHEN…….. is not near a whole # __ Moles__ smallest moles If ends in a decimal of Multiply ALL numbers by…. to get the Smallest Ratio ≈ 0.52 ≈0.33 or ≈0.663 ≈0.25 or ≈0.754 ≈0.2, ≈0.4, ≈0.6, ≈0.8 5

Empirical to Molecular Formula A compound has a molar mass of 60.0g/mol and its empirical formula is CH 2 O. Find the molecular formula. EmpiricalMolecular Formula Mass

Hebden Do Exercises 46 (d, g, & m) on pages 93 & Exercises 48 and 52 on page 95 of Hebden Read through Tutorial 5-1: Percent Mass and Empirical Formulas (Working in Pairs) Do the Self-Test on Tutorial 5-1