2. Equal volumes of gases at the same T and P have the same number of molecules. V = kn V and n are directly related. twice as many molecules MOLEY… MOLEY… MOLEY!!! V1 = V2 n1 n2

3. STP Values

4. Bring all the laws together PV=k V/T=k P/T=k V/n=k =kPVnT then k is given the variable R, and is called the Ideal Gas Constant So…

5. Brings together gas properties. Can be derived from experiment and theory. BE SURE YOU KNOW THIS EQUATION! P V = n R T

6. P = Pressure V = Volume T = Temperature N = number of moles Ideal Gas Constant R is a constant, called the Ideal Gas Constant memorize one convert the units to match R. Instead of learning a different value for R for all the possible unit combinations, we can just memorize one value and convert the units to match R. R = 0.08206 R = 0.08206 L atm mol K

7. How much N 2 is required to fill a small room with a volume of 960 cubic feet (27,000 L) to 745 mm Hg at 25 0 C? Solution 1. Get all data into proper units V = 27,000 L T = 25 0 C + 273 = 298 K P = 745 mm Hg (1 atm/760 mm Hg) = 0.980 atm And we always know R, 0.08206 L atm / mol K

8. How much N 2 is req’d to fill a small room with a volume of 960 cubic feet (27,000 L) to P = 745 mm Hg at 25 0 C? Solution Solution 2. Now plug in those values and solve for the unknown. PV = nRT n = 1.1 x 10 -3 mol RT RT RT RT n = (0.980 atm) (27,000 L) _ (0.08206) (298 K)

9. Dinitrogen monoxide (N 2 O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23°C, what is the pressure (mm Hg) in the tank in the dentist office? P(20.0 L) = (2.86moles)(0.08206)(296K) P = 3.47 atm P = 3.47 x 760 mmHg 1 atm P = 2640 mmHg

10. A 5.0 L cylinder contains oxygen gas at 20.0°C and 735 mm Hg. How many grams of oxygen are in the cylinder? (.97atm)(5.0L)=n(0.08206)(293K) 4.85 = 24.04n.20 moles = n.20 moles O 2 x 32.00 g O 2 1 mole = 6.4 grams O 2