Diffusion Particles of 2 or more substances mix spontaneously due to random motion How fast gases diffuse depends on: 1. speed of particles (KE) 2. Size of particles 3. attractive forces between particles Effusion Gas particles leaving a container through a small opening Movement caused by pressure

Pressure Can be used as conversion factors. Collisions on a surface 1 atm = 760 mm Hg = 760 torr = 101.325 kPa Can be used as conversion factors. 760 mm Hg 760 torr 1 atm 760 mm Hg 760 torr 101.325 kPa

Sample Problem A The average atmospheric pressure in Denver, Colorado is 0.830 atm. Express this pressure in millimeters of mercury (mm Hg).

Sample Problem B The average atmospheric pressure in Denver, Colorado is 631 mm Hg. Express this pressure in kPa.

Temperature Measure of the average kinetic energy of the molecules MUST ALWAYS be in Kelvin (K) ALWAYS! SERIOUSLY! K = ° C + 273

Combined Gas Law It’s a Before-After equation Look for words like “starts”, “begins”, “initial”, etc… Look for words like “ends”, “final”, “change”, etc… Look for the units to be mentionned twice Units don’t matter so long as they match EXCEPT for Temperature = Kelvin (K)

Combined Gas Law = P1 V1 T1 P2 V2 T2 P = Pressure (atm, mm Hg, torr, kPa) V = Volume (mL or L) T = Temperature (K)

Sample Problem C A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.0°C?

Sample Problem D A balloon has a volume of 40.0 L at 20 °C and 0.95 atm. At what temperature will the balloon expand to 50.0 L and 1.00 atm?

Boyle’s Law An equation Temperature is constant P1 V1 = P2 V2 When P increases, V decreases When P decreases, V increases Inversely proportional relationship

Sample Problem E A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant?

Charles’ Law An equation Pressure is constant V1 = V2 T1 T2 When T increases, V increases When T decreases, V decreases Directly proportional

Sample Problem F A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?

Gay-Lussac’s Law An equation Volume is constant P1 = P2 T1 T2 When T increases, P increases When T decreases, P decreases Directly proportional

Sample Problem G The gas in a container is at a pressure of 3.00 atm at 25°C. Directions on the container warn the user not to keep it in a place where the temperature exceeds 52°C. What would the gas pressure in the container be at 52°C?

A Summary All came from …

Ideal Gas Doesn’t really exist Exists with low numbers of molecules, high temp Explained by the Kinetic Molecular Theory

5 Assumptions of the Kinetic Molecular Theory Gases molecules are far apart. Gas molecules collide w/o losing energy. Gas molecules have kinetic energy because they move in constant, random motion There are no attraction / repulsion forces.

5 Assumptions of the Kinetic Molecular Theory Kinetic energy depends on T. Higher NRG  more KE  higher T At same T, all gas molecules of the same mass have exactly the same KE At same T, lighter gas molecules KE > heavier gas molecules KE

Ideal Gas Law Assuming all these to be true … P V = n R T P = pressure (atm) V = volume (L) n = # of mol R = 0.0821 L atm / mol K T = Temperature (K)

When Do I Use It? The variables are only mentionned ONCE. There has been no change in anything!

Sample Problem A What is the pressure in atmospheres exerted by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K?