1. Bell Ringer (on Friday) 1
Bell Ringer (on Friday) Aerosol cans can be dangerous if they are heated because they can explode. Suppose a can of hair spray with a pressure of 4.0 atm at a room temperature of 25oC is thrown into a fire. If the temperature of the gas inside the aerosol can reaches 402oC, what will be the pressure? Does this answer make sense??? 2. The volume of a gas is mL at 275 K and 92.1 kPa. Find its volume at STP.

2. Trade & Grade Task #2

3. Trade & Grade Task #2 272 kPa 113 mL 214 oC 479 K 676 K 1.75 atm
2.45 cm3
2.57 mol
1.53 mol
257 K
16.5 mL
20 L

4. Turn in Bell Ringer sheet to box Task #2 problems to box
Warning Labels to appropriate lab station. Make sure names of creators are on them!
Scenario A  Lab Station 1
Scenario B  Lab Station 2
Scenario C  Lab Station 3
Scenario D  Lab Station 4

5. Project Proposals
Due Monday – have what law you are doing and what type of model you are making
Gas Law choices
Boyle’s Law
Avogadro’s Law
Charles’ Law
Dalton’s Law
Gay-Lussac’s Law
Graham’s Law

6. Combined Gas Law Estimation Race

7. Avogadro’s Hypothesis
At the same temperature and pressure, equal volumes of gas have the same number of particles
1 mol of a gas=22.4 L
at STP
Standard Temperature & Pressure
0°C and 1 atm

8. Dalton’s Law of Partial Pressures
Partial pressure: pressure exerted by one gaseous component in a mixture
The pressure of a mixture of gases is simply equal to the sum of the partial pressure of each gas.
“Total Pressure = Sum of the Partial Pressures”
PT = P1 + P2 + P …

10. Dalton
1. A mixture of neon and argon gases exerts a total pressure of 2.39 atm. The partial pressure of the neon alone is 1.84 atm. What is the partial pressure of the argon?

11. Collecting Gas over water
When you collect a gas by water displacement, the collected gas also contains water vapor.
There is more water vapor at higher temperatures.

12. Gases Collect Over Water
Water Vapor Pressure Table
Temperature Pressure
(°C) (mmHg)

13. Dalton’s Law
Hydrogen gas is collected over water at 22.5°C. Find the pressure of the dry gas if the atmospheric pressure is 94.4 kPa.
The total pressure in the collection bottle is equal to atmospheric pressure and is a mixture of H2 and water vapor.
GIVEN:
PH2 = ?
Ptotal = 94.4 kPa
PH2O = 2.72 kPa
WORK:
Ptotal = PH2 + PH2O
94.4 kPa = PH kPa
PH2 = 91.7 kPa
Look up water-vapor pressure for 22.5°C.
Sig Figs for addition: Round to least number of decimal places.

14. Graham’s Law
Diffusion – spread of a gas throughout a space or second substance Effusion - The rate at which a gas escapes through a pinhole into a vacuum

15. Graham’s Law of Diffusion
The rate of diffusion of gases is inversely proportional to their molar masses.
r stands for rate (speed)
mm stands for molar mass of the gas

16. Let’s Practice
1. Determine the relative rate of diffusion for krypton and bromine. 2. A molecule of oxygen gas has an average speed of 12.3 m/s at a given temp and pressure. What is the average speed of hydrogen molecules at the same conditions? 3. An unknown gas diffuses 4.0 times faster than O2. Find its molar mass.