Gas Laws… Continued

The Combined Gas Law

Lets Review… Charles’ Law – volume and temperature Boyle’s Law – pressure and volume

Charles’ Law & Boyle’s Law Charles’ Law - Temperature and gas have a direct relationship. T↑ V↑ and T↓ V↓ Boyle’s Law - describes the indirect relationship between the pressure and volume of a gas. P↑ V↓ and P↓ V ↑

The Combined Gas Law The combined gas law is a gas law which combines Charles‘ law and Boyle's law. In the combined gas law, the volume of gas is directly proportional to the absolute temperature and inversely proportional to the pressure.

Cosmic gases

The Combined Gas Law Where: Equation: P1V1 = P2V2 T1 T2 P1 is the initial pressure V1 is the initial volume T1 is the initial temperature (in Kelvin) P2 is the final pressure V2 is the final volume T2 is the final temperature (in Kelvin)

Let’s Practice… Number 2 on Homework worksheet… A gas takes up a volume of 17 liters, has a pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas? P1 = P2 = V1 = V2 = T1 = T2 =

Ideal Gas An Ideal Gas (perfect gas) is one which obeys the ideal gas law exactly.

Ideal Gas An Ideal Gas is modeled on the Kinetic Theory of Gases which has 4 basic postulates: Gases consist of small particles (molecules) which are in continuous random motion The volume of the molecules present is negligible compared to the total volume occupied by the gas Intermolecular forces are negligible Pressure is due to the gas molecules colliding with the walls of the container

Real Gases Real Gases deviate from Ideal Gas Behavior because: at low temperatures the gas molecules have less kinetic energy (move around less) so they do attract each other at high pressures the gas molecules are forced closer together so that the volume of the gas molecules becomes significant compared to the volume the gas occupies Under ordinary conditions, deviations from Ideal Gas behavior are so slight that they can be neglected A gas which deviates from Ideal Gas behavior is called a non-ideal gas.

Cosmic and terrestrial gases

Ideal Gas Laws The ideal gas law is a combination of all the gas laws: Boyle’s, Charles’, Gay-Lussac’s The ideal gas law can be expressed as PV = nRT Where: P is the pressure in atm V is the volume in liters n is the number of moles R is a constant (0.0821 L atm /mol K) T is the temperature in Kelvin How do you calculate Kelvin?

Lets Practice… Number 1 on Homework worksheet If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 liters, what is the temperature? P = n = V = R = T = PV = nRT