The Gas Laws

Using temperature, pressure, and volume, there are 3 basic gas laws: Boyle’s, Charles’s, and Gay-Lussac’s

Boyle’s Law

If the temperature is kept constant, the pressure and volume are inversely proportional. P. 369

Boyle’s Law If the temperature is kept constant, the pressure and volume are inversely proportional. P. 369 and 370 PV = k k is a constant and is the same no matter what gas, as long as the temperature and the amount of gas stay the same.

Boyle’s Law If the temperature is kept constant, the pressure and volume are inversely proportional. PV = k Since the pressure times the volume always equals the same constant, even if the pressure or the volume is changed (as long as the temperature and amount of gas is constant) the new PV will equal the original PV P 1 V 1 = P 2 V 2

Example 1: 1.00L of a gas at standard temperature and pressure is compressed to 473mL. What is the new pressure of the gas?

Example 2: The highest pressure ever produced in a laboratory setting was about 2.0 x 10 6 atm. If we have a 1.0 x L sample of a gas, at that pressure, then release the pressure until it is equal to atm, what would be the new volume of that gas?

Charles’s Law

If the pressure and amount of gas are kept constant, the volume and the temperature are directly proportional. p. 371 and 372 The temperature has to be in Kelvin. Why?

Charles’s Law If the pressure and amount of gas are kept constant, the volume and the temperature are directly proportional. The temperature has to be in Kelvin. 0ºC = 273 K To change from Celsius to Kelvin, add 273. To change from Kelvin to Celsius, subtract 273.

Charles’s Law If the pressure and amount of gas are kept constant, the volume and the temperature are directly proportional. V/T = k V 1 / T 1 = V 2 / T 2

Example 3: On hot days you may have noticed that potato chip bags seem to inflate, even though they have not been opened. If I have a 250 mL bag at a temperature of 19ºC, and I leave it in my car which has a temperature of 60ºC, does the bag expand? To what size?

Example 4: A soda bottle is flexible enough that the volume of the bottle can change even without opening it. If you have an empty soda bottle (volume 2.0 L) at room temperature (25ºC), what will the new volume be if you put it in your freezer (-4ºC)?

Gay-Lussac’s Law

If the volume and amount of gas are kept constant, the pressure and temperature are directly proportional. p. 373 P/T = k P 1 / T 1 = P 2 / T 2

Example 5: A gas has a pressure of mmHg at 40ºC. What is the temperature at standard pressure, if the volume is kept constant ?

Example 6: Calculate the final pressure inside a scuba tank after it cools from 1.00 x 10 3 ºC to 25ºC. The initial pressure in the tank is 130 atm.

Combined Gas Law Boyle’s, Charles’s, and Gay-Lussac’s can be combined into one law. P 1 V 1 = P 2 V 2 T 1 T 2

Example 7: What is the volume at STP of 720 mL of a gas collected at 20 ºC and 3 atm?

Example 8: 690 mL of oxygen are collected over water at 26 ºC and a total pressure of 725 mmHg. What is the volume of the dry oxygen at 52 ºC and 800 mmHg?

 p.367 #1 (You will need table on p. 859)  p. 370 #1  p. 372 #1 and 2  p. 374 #1, 2, and 3  p. 375 #1 and 2