Warm Up #5 Find the percent composition of the following: C12H22O12 (A big sugar) Fe2O3 (Iron (III) Oxide) H2O2 (Hydrogen Peroxide)

Warm Up #4 You have a 9.0 gram sample of gaseous hydrogen peroxide (H2O2) How many hydrogen peroxide molecules are present in this sample? What is the volume of this hydrogen peroxide in Liters? In milliliters? Find the molar mass of H2O2. TRY to figure out what percentage of this mass is Oxygen.

Molecular and Empirical Formulas Chapter 10.4 Molecular and Empirical Formulas

Empirical Formula Empirical Formula – the simplified ratio of elements in a compound Ex. C6H12O6 Empirical Formula: CH2O (1:2:1 ratio)

= 1.85 mol N = 4.63 mol O Example Problem Given: 25.90% = Nitrogen 74.10% = Oxygen Step 1: Convert to Moles (assume 100 g) 25.90 g N 1 mol N 14.01g N 74.10 g O 1 mol O 16.00 g O = 1.85 mol N = 4.63 mol O

Example Problem Cont’d Next Step: Find the Mole to Mole Ratio (2.5 mol O : 1 mol N) Last Step: If ratio = not a whole number, make it a whole number (ex. multiply by 2) 5 mol O: 2 mol N Empirical Formula: N2O5 4.63 mol O = 2.50 ratio 1.85 mol N

Empirical vs. Molecular Formula Remember: Empirical Formula = MOST basic formula of compound Molecular Formula = ACTUAL formula of compound Difference: Molar Mass (given)

Empirical to Molecular Example: Empirical: N2O5 Mass = 108.02 g Actual Mass = 324.06 g 3 x the mass of the empirical Molecular Formula: N6O15 Multiply both subscripts by 3