1. DO NOW! On Notebook Paper…
What is the percent composition of carbon in C14H18N2O5 ?
What is the empirical formula for a compound that contains 42.05% nitrogen and 95.95% oxygen?
What is the empirical formula for a compound that contains 13.5% Ca, 10.8% O, and 0.675% H? 

2. Unit: Chemical Quantities
Notes
Unit: Chemical Quantities
Determining the Molecular Formula from the Empirical Formula

3. After today, you will be able to…
Calculate the empirical formulas for various compounds given their percent makeup

4. Molecular Formula Determination from the Empirical Formula
To determine molecular formulas from the empirical formula follow these steps:
First determine the empirical formula
Use the formula:
Multiply the subscripts in the empirical formula by this whole number to get the molecular formula
Molar mass of molecular formula
Molar mass of empirical formula

5. Example: What is the molecular formula for a compound that is 74
Example: What is the molecular formula for a compound that is 74.0% C, 8.70% H, and 17.3% N and has a molar mass of g?
70.4gC
8.70gH
17.3gN
1 mol C
12.01gC
6.16
Empirical: C5H7N x = = 5
1.23
5C=12.01(5) =
1 mol H
1.01gH
8.61
7H=1.01(7) = x = = 7
1.23
1N=14.01(1) =
1 mol N
14.01gN
1.23
81.07 x = = 1
1.23
243.39
81.07 = 3
x C5H7N
C15H21N3

6. WS #5:What is the molecular formula for a compound that is 34
WS #5:What is the molecular formula for a compound that is 34.31% sodium, 17.93% carbon, 47.76% oxygen and has a molar mass of g?
34.31gNa
17.93gC
47.76gO
1 mol Na
22.990gNa
1.49
Empirical: NaCO2 x = = 1
1.49
1Na = (1) = 22.99
1 mol C
12.011gC
1.49
1C = (1) = x = = 1
1.49
2O =15.999(2) =
1 mol O
15.999gO
2.99
66.999 x = = 2
1.49
134.00
66.999 = 2
x NaCO2
Na2C2O4

7. Time to Practice! Complete WS
HOMEWORK:
Time to Practice! Complete WS

8. DOL Write the molecular formulas of the following compounds:
A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole.
The compound benzamide has the following percent composition. What is the empirical formula?
C = % H= % O = % N= %
A component of protein called serine has an approximate molar mass of 100 g/mole. If the percent composition is as follows, what is the empirical and molecular formula of serine?
C = % H= % O = % N= %