1. Unit 3, Lesson 8: Finding Empirical Formulae

2. The Empirical Formula
The empirical formula is the smallest whole-number ratio of atoms that represents the molecular composition of a species.
For example, the molecules CH2, C2H4, and C3H6 all have the empirical formula CH2.
5 min

3. Finding the Empirical Formula
This is basically the opposite of finding percentage composition.
Example: What is the empirical formula of a compound consisting of 80.0% C and 20.0% H?
Now You Try: A compound contains 58.5% C, 7.3% H, and 34.1% N. What is the empirical formula of the compound?
15 min

4. Brain Break!

5. What to do with decimals...
Fraction
0.50
0.33
1/3
0.67
2/3
0.25
0.75
0.20
1/5
0.40
2/5
0.60
3/5
0.80
4/5
Example: What is the formula of a compound containing 81.8% C and 18.2% H?
Your Turn: What is the empirical formula of a compound containing 39.0% Si and 61.0% O?
15 min

6. Homework
Pg. 93 #46 odd letters
5 min