II Gas Laws – a series of controlled experiments with the four variables (listed below) that define the physical properties of a gas
Moles
Temperature
Volume
Pressure
1) Boyles Law- Volume of a gas is inversely proportional to the pressure exerted by the gas.
A) Pressure and Volume are variables, moles and temperature controls
P1V1 = P2V2
(This is why your ears hurt when you dive to the bottom of swimming pool.)
2) CharlesÕs Law – Volume of a gas is directly proportional to the temperature of the gas in ûK.
A) Volume and Temperature are variables, moles and pressure are controls.
V1/T1 = V2/T2
3) AvagadroÕs Law- Volume of a gas is directly proportional to the moles of gas
A) Volume and moles are variables, temperature and pressure are controls.
V1/n1 = V2/n2
This is how you inflate a balloon.
4) JohnÕs Law-Pressure of a gas is proportional to the temperature of the gas in ûK.
A) Pressure and Temperature are variables, moles and volume are controls.
P1/T1 = P2/T2
This is why you do not throw an aerosol can into the fire.
5) Combined Gas Law- This law combines all the laws above. The combined gas law is very useful because it can be used to derive any of the controlled experiment laws. The combined gas law allows you to investigate experiments in which there are more than two variables.
A)
P1V1/n1T1 = P2V2/n2T2
6) Ideal Gas Law- the combined gas law written in another form. (Ignore this one for now, we will come back to it, when it is more useful.)
PV = nRT
Gas Laws
Practice
Potentially Useful Information: 1 atm= 760 mmHg= 101.3 kPa
C + 273 = K
Sample problems next page- PROBLEM PARTY!! Work together with your table group. Show your work on a separate sheet of paper. Show the algebraic form of the law you use to solve the problem, then show your work with data, circle your final answer, include units, and significant figures. Check your answers and be sure all members of the group understand before proceeding to the next questions.
1) It is claimed that the highest pressure ever produced in a laboratory setting was about 2.00 x 106 atm. If we have a 1.00 x 10-5 liter sample of a gas at that pressure, then release the pressure until it is equal to 0.275 atm, what would the new volume of that gas be?
2) A soda bottle is flexible enough that the volume of the bottle can change even without opening it. If you have an 2.00 liter bottle filled with air at room temperature (25.00C), what will the new volume be if you put it in your freezer (-4.00 0C)?
3) Aerosol cans carry warnings on their labels that say not to incinerate them or store cans above a certain temperature. The gas in a use aerosol can is at a pressure of 103 kPa at 25.0¼C. If the can is thrown onto a fire, what will the pressure be when the temperature reaches 928¼C? Translate your answer to atm and ponder the meaning.
4) Atmospheric pressure on the peak of Mt. Everest can be as low as 0.197 atm, which is why climbers need to bring oxygen tanks for the last part of the climb. Average temperature at the peak is -36 C. If the climbers carry 50.0 liter tanks with an internal gas pressure of 204 atm at a temperatue of -36 ûC, what will be the volume of the gas when it is released from the tanks to the climbers lungs at a temperature of 37 ûC and a pressure of .197 atm?
5) The pressure in a car tire is 1.95 atm at 27.0¼C. After a long drive the pressure is 2.22 atm. Assuming a constant volume, what is the temperature of the air in the tire after the drive?
6) Gases dissolve better in liquids under pressure. Divers get Òthe bendsÓ if they come up too fast because gas dissolved in their blood forms bubbles which then expand as they come up from depth. If a .00020 liter bubble is formed at a depth of 132ft where the pressure is 5.00 atm, what will the volume of the bubble be when the diver reaches the surface where the pressure is 101.3 KPa.
7) On hot days, you may have noticed that potato chip bags seem to ÒinflateÓ, even though they have not been opened. If I have a 250.0 mL bag at a temperature of 19.00C, and I leave it in my car that has a temperature of 60.00 C, what will the new volume of the bag be?
8) You decide to complete the most uncontrolled experiment possible. You take a balloon with a volume of 22.4 liters that contains 1.00 moles of a gas at a pressure of 1.00 atm and a temperature of 0.00 ûC. You take the balloon and add another 6.022 x 1023 molecules of He, you now put the balloon in your new pressurized-oven. You adjust the pressure so it will 570 mmHg and the temperature will be 346 ûC. Find the volume of balloon in the oven. Why is this not considered a controlled experiment?