1. Empirical and Molecular Formula
Mrs. Paparella
December 22, 2014

2. Empirical Formula
Simplified formula that shows the minimum ratio of elements in a compound
Can be the same as the molecular formula, if the molecular formula can’t be reduced to a simplified form
Examples: CH2, CH3, CH2O

3. Molecular Formula
The true formula of a compound that shows the exact number of each element in the compound.
Ex: C6H12O6 is glucose
C10H14N2 is nicotine
Sucrose is C12H22O11

4. Practice Set
What is the empirical formula for the following molecular formula?
C6H12O6
C10H14N2
C12H22O11
C10H22 (decane)
C8H14 (octene)
C5H (pentane)
C9H8O4 (aspirin)
C4H (butene)
C27H44O (vitamin D)
C6H8O6 (vitamin C)

5. Use the formula n=Molecular Mass Empirical Mass
How to Mathematically Determine the Molecular Formula given Empirical Formula and Molecular Mass
Use the formula
n=Molecular Mass
Empirical Mass
To find the n value which is the multiplier # that states the relationship between the empirical and molecular formula
To find the empirical mass you need to use the Periodic Table to look up the atomic masses of each element and figure out the total empirical mass.

6. Now distribute the 7 through the empirical formula
Heptene has the formula mass of 98 amu, and it has the empirical formula of CH2. WhAT IS HEPTENE’S MOLECULAR FORMULA?
Figure out the empirical mass using the PT. C= 1 x 12 =12 H= 1 x 2= = 14 amu (can use g/mole as well as amu)
Substitute into
n=Molecular Mass
Empirical Mass
n = 98 amu = 7
14 amu
Now distribute the 7 through the empirical formula
(CH2)7 = C7H14

7. Practice
1. Find the molecular formula of a compound with a molecular mass of 56 g/mole and an empirical formula of CH2

8. Answer C = 1 x 12= 12 H= 2 x 1= 2 12 +2 = 14 g/mole n= 56/14 = 4
(CH2) 4 = C4 H8