1. 5.4 – 5.5: Applying The Ideal Gas LawPV
----- nT

2. The Ideal Gas Law
If we combine the three simple gas laws, we end up with a proportionality constant known as the ideal gas constant(R): PV
R = nT
By plugging in values for pressure, volume, temperature and moles at STP, we receive the ideal gas constant (located on your reference table). MAKE SURE YOU CHECK UNITS WHEN USING THIS CONSTANT!!!
The ideal gas law: PV = nRT  also locate on your reference table

3. Let’s Try a Sample Problem
An 8.50 L tire contains mol of gas at a temperature of 305 K. What is the pressure (in atm) of the gas in the tire? nRT (0.552 mol) ( L atm / mol K) (305 K) P = = V 8.50 L P = 1.63 atm

4. Let’s Try Another
What volume does mol of gas occupy at a pressure of 715 mmHg and a temperature of 58oC? nRT (0.556 mol)(62.36 L mmHg / mol K)(331K) V = = P 715 mmHg V = 16.1 L

5. Molar Volume and Molar Density
If we were to rearrange the ideal gas law to solve for volume at STP (ST = 0oC or 273 K) and (SP = 1.00 atm or 760 mmHg) we end up with the volume of a mole of any gas! Molar volume = 22.4 L What is the formula for density? What are the units when referring to a liquid or gas? m (in grams) D= V (in liters) With this formula, you can see that the molar mass of a gas over molar volume of that same gas, is the gases molar density(d). Molar density is directly proportional to molar mass (M). PM Therefore: d = RT

6. Let’s Try a Sample Problem
Calculate the density of xenon gas at a pressure of 742 mmHg and a temperature of 45oC. PM (742 mmHg)( g/mol) d = = RT (62.36 L mmHg / mol K)(318 K) d = 4.91 g/L

7. Let’s Try Another
A sample of gas has a mass of 827 mg. Its volume is L at a temperature of 88oC and a pressure of 975 mmHg. Find the molar mass.
dRT ((0.827 g/0.270 L)(62.36 L mmHg / mol K)(361 K)
M = =
P mmHg
M = 70.7 g/mol

8. Chapter 5 pgs. 239-240 #’s 38, 40, 44, 56, & 58 Read 5. 6-5. 7 pgs