Warm up (12/5) Lab 7 out in lab books, book HW out in your notes! Consider another balloon that starts out at a volume of 4.3 L at STP. When the balloon is released outside, it rises until it pops at a pressure of 0.24 atm and a temperature of 4.0 C. What was the final volume of the balloon before it popped? ASSUMPTIONS?? 18 L

Debrief Lab 7 Molar Mass Results?

One thing you need to know… “STP” Standard Temperature and Pressure P = 100 kPa T = 273 K, or O °C Solve for molar volume of a gas at STP = 22.7 L

Molar Volume of a Gas At STP, any gas has a volume of: ??? L! Why? Not really something you have to memorize (because PV=nRT gives you that) Why? Use 100 kPa and 273K = 22.7 L of one mole of ANY gas! Because, like Avogadro said, all gas particles are SO SMALL in relation to the size of their container (mostly empty space) that the difference in size/mass of particles does not matter at all.

Combined Gas Laws and concepts If you have a hard time figuring out the relationships (or remembering them):

Combined gas laws When a 1.54 L bike tire, pumped to 705 kPa, starts out at the beginning of a ride, the gas inside the tire is at a temperature of 21.5 C. Throughout the ride, the temperature increases to 23.5 C and the volume expands slightly to 1.55 L. What is the new pressure inside the tire? P = 97.6 psi

Gas applications: Molar Mass What is the formula (units) for molar mass? So, in any problem, if we know the grams and the number of moles, we can find an unknown molar mass!

Gas applications: Molar Mass A sample of gas has a volume of 445 cm3 and a mass of 1.500 g at a pressure of 95 kPa and a temperature of 28°C. What is its molar mass? Solve for moles, and then plug in molar mass = grams / moles = 89 g/mol

Gas applications: Density Recall the equation for density? If a sample of hydrogen gas is held in a 2.5 L flask at 560 K and a pressure of 4.3 atm, what is the density of the gas? 0.19 g/L

Demo time! Write down explanation of what happened (USE PICTURES and EXPLAIN using your observations as justification)! Can crush, can do shaving cream for fun in VC

Worksheet Day 10 work time Some good, clean gases practice! Remember, QUIZ next class! Don’t forget: R = 0.08206 L atm/mol K = 8.314 L kPa/mol K

Homework Day 10 Finish WS Day 10 and Lab 7 Error Analysis Book written problem in back of chapter: 23 (write it out well) Quiz next class! STUDY!