1. Empirical Formulas

2. Empirical formula –
lowest whole-number ratio of the elements in a compound
(divide by – Greatest Common Factor)
What is the empirical formula of C2N2H8
CNH4

3. Empirical Formula Calculations
1.) Change the given information to moles for each element.
2.) Divide each mole answer by the smallest number of moles.
3.) If the answers from step 2 are not whole numbers then divide by the smallest decimal part.
4.) Write the formula with the mole ratio as subscripts.

4. EX 1 Find the empirical formula.
A compound contains g of Ag and 0.69g of O.

5. Ag2O

6. EX 2 A compound contains 25.9% N and 74.1% O.
Find the empirical formula.

7. Nitrogen = 1 ÷ 0.5 = 2
Oxygen = 2.5 ÷ 0.5 = 5
N2O5

8. MOLECULAR FORMULAS

9. Molecular formula – empirical formula or its multiple
Several compounds can have the same empirical formula but different molecular formulas.
What is the empirical formula of C2N2H8?
CNH4
What is the molecular formula of CNH4?
C2N2H8

10. Convert molecular  empirical
Divide subscripts by greatest common factor
Convert empirical  molecular
multiply subscripts by …

11. EX 1
The empirical formula is CH4N and the molar mass is 60.0 g. Find the molecular formula.
C 1 X 12.0 = 12.0g
4H 4 X = 4.0g
N 1 X = 14.0g
30.0g
C2H8N2

12. EX 2
Find the molecular formula of C4H6O if the molar mass is 280.0g.
4C 1 X 12.0 = 48.0g
6H 4 X = 6.0g
O 1 X = 16.0g
70.0g
C16H24O4