1. 3.10.7 Density and Ideal gas law
Unit 3: Gases, Liquids, Solids, Solutions and Electrochemistry
Density and Ideal gas law
Textbook 10.5

2. Learning Objectives: SWBAT:
Big Idea 2: Chemical and physical properties of materials can be explained by the structure and the arrangement of atoms, ions, or molecules and the forces between them. Students will be able to demonstrate understanding by laboratory investigation, analysis of data and creation of models.
Learning Objectives:
SWBAT:
Calculate the density or molecular mass of a gas

3. What is the density of NH3 at 800. torr and 25 C?
PV= nRT
Rearrange:
P = n
RT V
Density = mass/volume
How can we get n to be mass????

4. What is the density of NH3 at 800. torr and 25 C?
Molar mass = g/mol Or Molar mass = mass/mol
So….
Mol = mass/molar mass
n = mass/molar mass

5. What is the density of NH3 at 800. torr and 25 C?
n = mass/molar mass
PV=nRT
PV = (mass/molar mass) RT…rearrange
mass/V = molar mass (P)/RT Or
Density = molar mass (P)/RT
In gases density units g/L (not g/mL like everything else)

6. What is the density of NH3 at 800. torr and 25 C?
Density = molar mass (P)/RT
= (17g/mol) (800torr)
(62.4 L torr) (298K)
mol K
= .73g/L

8. References http://www.sciencegeek.net/Chemistry/Powerpoints2.shtml
I modified his original PPT to fit our needs in AP Chemistry needs.
Our textbook: Brown, Lemay et all. AP edition chemistry, 13th edition, 2015