1. 6.7 Empirical Formula and 6.8 Molecular Formulas

2. - ex. The empirical formula for water is H2O
Empirical formula: a formula that gives the lowest ratio of atoms is a compound
- ex. The empirical formula for water is H2O
Molecular Formula: a formula that gives the actual number of atoms in one molecule of a compound
it may be the same as the empirical formula or a multiple of this formula
- ex. The molecular formula for hydrogen peroxide is H2O2; its empirical formula would be HO

3. Determining the Empirical Formula of a Compound
1-“Percent to mass”
2- “Mass to mole”
3- “Divide by small”
4- “Multiply 'til whole”

4. Ex. 1: A compound consists of 72. 2% magnesium and 27
Ex. 1: A compound consists of 72.2% magnesium and 27.8% nitrogen by mass. What is the empirical formula?
1. Percent to mass: Assume 100 g of the substance, then
2) Mass to moles:

5. 3) Divide by small: 4) Multiply 'til whole-

6. Calculating the Molecular Formula of a Compound
The empirical formula of the compound is C4H6O and has a molar mass of 140 g/mol. What is the Molecular Formula of the compound?
1) Calculate the molar mass (M) of the empirical formula:
2) Divide the molecular weight by the empirical formula molar mass
3) Multiply the subscripts of the empirical formula by the factor just computed .

7. Homework
Pg. 293 # 1-9
Pg. 300 # 1-4, 6-7