DO NOW! On Notebook Paper… What is the percent composition of carbon in C14H18N2O5 ? What is the empirical formula for a compound that contains 42.05% nitrogen and 95.95% oxygen? What is the empirical formula for a compound that contains 13.5% Ca, 10.8% O, and 0.675% H? 

Unit: Chemical Quantities Notes Unit: Chemical Quantities Determining the Molecular Formula from the Empirical Formula

After today, you will be able to… Calculate the empirical formulas for various compounds given their percent makeup

Molecular Formula Determination from the Empirical Formula To determine molecular formulas from the empirical formula follow these steps: First determine the empirical formula Use the formula: Multiply the subscripts in the empirical formula by this whole number to get the molecular formula Molar mass of molecular formula Molar mass of empirical formula

Example: What is the molecular formula for a compound that is 74 Example: What is the molecular formula for a compound that is 74.0% C, 8.70% H, and 17.3% N and has a molar mass of 243.39g? 70.4gC 8.70gH 17.3gN 1 mol C 12.01gC 6.16 Empirical: C5H7N x = = 5 1.23 5C=12.01(5) = 60.05 1 mol H 1.01gH 8.61 7H=1.01(7) = 7.07 x = = 7 1.23 1N=14.01(1) = +14.01 1 mol N 14.01gN 1.23 81.07 x = = 1 1.23 243.39 81.07 = 3 x C5H7N C15H21N3

WS #5:What is the molecular formula for a compound that is 34 WS #5:What is the molecular formula for a compound that is 34.31% sodium, 17.93% carbon, 47.76% oxygen and has a molar mass of 134.00g? 34.31gNa 17.93gC 47.76gO 1 mol Na 22.990gNa 1.49 Empirical: NaCO2 x = = 1 1.49 1Na = 22.990(1) = 22.99 1 mol C 12.011gC 1.49 1C =12.011 (1) = 12.011 x = = 1 1.49 2O =15.999(2) = +31.998 1 mol O 15.999gO 2.99 66.999 x = = 2 1.49 134.00 66.999 = 2 x NaCO2 Na2C2O4

Time to Practice! Complete WS HOMEWORK: Time to Practice! Complete WS

DOL Write the molecular formulas of the following compounds: A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. The compound benzamide has the following percent composition. What is the empirical formula? C = 69.40 % H= 5.825 % O = 13.21 % N= 11.57 % A component of protein called serine has an approximate molar mass of 100 g/mole. If the percent composition is as follows, what is the empirical and molecular formula of serine? C = 34.95 % H= 6.844 % O = 46.56 % N= 13.59 %