Bell Ringer (on Friday) 1 Bell Ringer (on Friday) 1. 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 200.0 mL at 275 K and 92.1 kPa. Find its volume at STP.

Trade & Grade Task #2

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

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

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

Combined Gas Law Estimation Race

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

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 + P3 + …

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?

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.

Gases Collect Over Water Water Vapor Pressure Table Temperature Pressure (°C) (mmHg) 0.0 4.6 5.0 6.5 10.0 9.2 12.5 10.9 15.0 12.8 15.5 13.2 16.0 13.6 16.5 14.1 17.0 14.5 17.5 15.0 18.0 15.5 18.5 16.0 19.9 16.5 19.5 17.0 20.0 17.5 20.5 18.1 21.0 18.6 21.5 19.2 22.0 19.8 22.5 20.4 23.0 21.1 23.5 21.7 24.0 22.4 24.5 23.1 25.0 23.8 26.0 25.2 27.0 26.7 28.0 28.3 29.0 30.0 30.0 31.8 35.0 42.2 40.0 55.3 50.0 92.5 60.0 149.4 70.0 233.7 80.0 355.1 90.0 525.8 95.0 633.9 100.0 760.0

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 = PH2 + 2.72 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.

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

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

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.

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