1. Warm up (10/17) Lab 5 out and open, please!
Please access the Google Doc to enter your results!
A container has 10. grams of N2, 100. grams of Xe, and 42 grams of Ar. What is the Ptotal in the container if the volume is 4.0 L and the temperature is 50. °C?
nN2 = moles nXe = moles nAr = moles ntotal
= 2.17 moles
Ptotal = 14.4 atm (if you add)

2. Lab 5 debrief What did you get for your R value?
What was your biggest source of error?
How could you fix it?

3. Combined gas laws
When a 1.54 L bike tire, pumped to 102 psi, starts out at the beginning of a ride, the gas inside the tire is at a temperature of C. Throughout the ride, the temperature increases to C and the volume expands slightly to 1.62 L. What is the new pressure inside the tire?
97.6 psi

4. Combined gas laws
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

5. Tube demo!
Can you explain WHY?

6. Manometers and Barometers
P = Patm + or – h of tube

7. Try it!
If the atmospheric pressure today is 754 mmHg, and the height (h) of the mercury in the tube is 125 mm, what is the pressure inside the tube?
629 mmHg

8. Stoichiometry with gases! (5.4)
Not too difficult, just use PV=nRT when needed to solve for moles (instead of g  mol)
When octane (C8H18) is combusted:
Give the balanced chemical equation
If a 2.35 g sample of octane is fully combusted, what is the pressure in atmospheres of the products in the 2.5 L flask and 450 K?
5.2 atm

9. Gas applications: Density (5.4)
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

10. Lab 5 - Molar Volume of a Gas at STP (Avogadro’s work)
At STP, any gas has a volume of: L!
Not really something you have to memorize (because PV=nRT gives you that)
Why?
What is the density of each gas?
Gas molecules are so tiny and pressure doesn’t depend on mass (really) – the number of particles is what affects pressure! So, equal volumes at equal conditions of gases have the same number of moles! Super important!

11. Vapour Pressure Reminder!
Vapour pressure: how many molecules have enough energy to get into gas phase at any given temperature.
Iodine?

12. Lab #6: Unknown Volatile Liquid ID by Vapor Pressure

13. Lab #6: Vapor Pressure of a Volatile Liquid
Application of PV = nRT
Find the molar mass of the unknown and identify it based on the list of possibilities!

14. Lab 6 – Pre-Lab Work Time
Needs to be done for lab Tomorrow!

15. Homework Unit 2 Day 3 Webassign Gases 1: due THURSDAY by 8am
Lab 6 due: Monday
All post-lab questions (1-7) in lab book
Use chemical information sheet on Moodle to ID your unknown
Quiz 1: Monday!