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

2. 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.

3. Molecular and Empirical Formulas
Chapter 10.4
Molecular and Empirical Formulas

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

5. = 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 mol N
14.01g N
74.10 g O 1 mol O
16.00 g O
= 1.85 mol N
= 4.63 mol O

6. 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

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

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