4. PhET Partial Pressures Simulation
Unit 9: Stoichiometry
PhET Partial Pressures Simulation

5. PhET: Partial Pressures Simulation
Q: What is the relationship between pressures of two individual gases at constant temperature and volume and the pressure of a mixture of both gases under the same conditions.
Note:
Record the range of values in the Data section
Calculate the average pressure with the uncertainty associated with the recorded range of values and record in the Evaluation section

6. Some things you need to know (remember)
Standard temperature:
0 °C or 273 K
Which one should you use with gas laws?
T (K) = T (°C) + 273
Standard pressure:
101.3 kPa
1.00 atm
760 mm Hg

7. Relationships

8. Combined Gas Law What if we combine all of the relationships?
What has to be held constant?

9. What about different gases?
N particles A
2N particles B
How do the pressures in the containers compare to each other?
What if we put the two gases together in the same container?
What fraction of the pressure is due to:
A? (1/3)
B? (2/3)

10. Gas Mixtures Each gas contributes to the total pressure
By mole fraction (or percentage)
Dalton’s Law of Partial Pressures:

11. Vapor Pressure The pressure exerted by a gas over its liquid
A partial pressure
Depends on temperature
Determined experimentally
Remember the density of CO2 lab?
How did we collect the CO2?
What’s the pressure of “dry” CO2?

12. Patm=730 mm PCO2=? PH2O= 20.1 mm (from chart) %CO2=?
When you found the density of carbon dioxide gas, you collected the gas by displacing water in a bottle. The gas you collected was a mixture of CO2 and H2O vapor. If, on the day of the lab, the room pressure were 730 mm Hg and the temperature in the room was 22.2°C, a. What would be the partial pressure of the “dry” carbon dioxide gas? b. What fraction of the mixture was CO2?
Patm=730 mm
PCO2=?
PH2O= 20.1 mm (from chart)
%CO2=?

13. Assignment Finish the PhET assignment Unit 9 WS #1
Gas Properties
Unit 9 WS #1
Lab 9.1 Molar Volume of a Gas
Next Monday