1. Unit 3, Lesson 9: Finding Molecular Formulae

2. Finding the Molecular Formula
The molecular formula tells us the actual number of atoms in a molecule. It is a multiple of the empirical formula. For example, C3H6 is CH2 times a multiple of 3.
To find out the multiple, we use the equation:
multiple = molar mass / empirical mass
(the empirical mass is just the molar mass of the empirical formula)

3. Finding the Molecular Formula
Example: A molecule has an empirical formula of HO and a molar mass of 34.0 g. What is the molecular formula?
Practice Problem #1: The empirical formula of a compound is SiH3. If mol of a compound has a mass of 1.71 g, what is the compound’s molecular formula?
15 min

4. Brain Break!

5. Practice Problem #2: A gas has the empirical formula POF3. If 0
Practice Problem #2: A gas has the empirical formula POF3. If L of the gas at STP has a mass of 1.62 g, what is the molecular formula of the compound?
10 min

6. Homework
Pg. 95 #47-55 odd numbers
10 min