# Chapter 5 Lecture Problems

## 5.3 The SimpleGas Laws: Boyle's Law, Charles's Law, and Avogadro's Law

1. Pressure and volume; Boyle's Law. Given an initial volume of 350 in3 and a compression ratio of 10:1, what is the final volume? Solution.
2. Pressure and temperature. A pressure cooker starts out at 25 C and 1 atm pressure. What is the pressure at 200 C? Solution
3. Volume and temperature; Charles' Law: 1 m3 of steam is heated from 100 C to 500 C at constant pressure. What is the final volume? Solution
4. Combined Gas Law; A stratospheric sampling balloon starts at sea level, 760 torr and 20 C with a volume of 1000 m3. The balloon rises to a pressure altitude of 1000 Pa (appx 40 km) where the temperature is -40 C. What is the volume of the balloon at this altitude? Solution

## 5.4 The Ideal Gas Law

1. Gas data for 1 gram at STP. Calculate the molar volume
1. H2 11.1 L
2. He 5.57 L
3. N2 0.800 L
4. Cl2 0.316 L
5. Solution

2. A stratospheric sampling balloon starts at sea level, 760 torr and 20 C with a volume of 1000 m3. The balloon rises to a pressure altitude of 1000 Pa (appx 40 km) where the temperature is -40 C. What is the volume of the balloon at this altitude? How many moles of He are in the balloon, what is the mass of the He in the balloon. Solution

## 5.5 Applications of the Ideal Gas Law: Molar Volume, Density and Molar Mass of a Gas

1. A 250 mL Erlenmyer Flask is weighed on an analytical balance; mass = 158.2376 g
2. The flask is filled with water at 20 oC and weighed on an analytical balance; mass = 420.9165 g
3. The flask is emptied and throughly dried.
4. Next 10.0 mL of a liquid is added to the flask, the mouth of the flask is covered with foil and a pin hole made in the foil.
5. The flask is placed in a water bath and heated to 95 oC for 20 minutes until no liquid is observed in the flask.
6. The flask is cooled to room temperature, vapor is observed to consdense in the flask, the temperature is measured T = 20 oC
7. The flask is weighed on an analytical balance; mass = 158.8714 g
Determine the molecular weight of the unknown liquid.

## 5.6 Mixtures of Gases and Partial Pressures

A gas manifold connects three flasks. The first flask contains 1.0 L of He at 180 torr. The second flask contains 1.0 liters of Ne at 0.45 atm. The third flask contains 2.0 L of Ar at 25 kPa. Calculate hte partial pressure of each gas and the total pressure when the manifold is opened. (From Zumdahl, Chemistry)

## 5.7 Gases in Chemical Reactions: Stoichiometry Revisited

1. Given 100 g of NaN3, what is the final volume of the air bag at 783 torr and 15 C? The air bag is show in this video; ( Internet© Saunders, 1997) The reaction for an air bag is:
2NaN3(s) --> 2Na(s) + 3 N2(g)
Solution

## 5.10 Real Gases: The Effects of Size and Intermolecular Forces

1. Calculate the pressure for 0.01, 0.1, 1.0, 10, 100 moles of an ideal gas in a 1 liter container at 273.15 K. Also calculate the pressure of He and CO2 using the Van der Walls Equation to account for non-ideal behavior.
2. Calculate the pressure for 0.1 moles of an ideal gas in a 1 liter container at 100, 200, 400 and 800 K. Also calculate the pressure of He and CO2 using the Van der Walls Equation to account for non-ideal behavior.
Van der Waals Constants (From Zumdahl, 4th ed)
Gas a (atm*L2 * mol-2) b (L mol-1)
He 0.0341 0.0237
Ne 0.211 0.0171
Kr 2.32 0.0398
N2 1.39 0.0391
CO2 3.59 0.0427
Solution