1. Ideal Gases Prentice-Hall Chapter 14.3 Dr. Yager

2. Objectives  Compute the value of an unknown using the ideal gas law  Compare and contrast real and ideal gases

3. Ideal Gas Law P x V = n x R x T (also written PV=nRT) P = pressure; atm or kPa (depending on R) V = volume; L n = moles; mol T = temperature (Kelvin) R = gas constant (Must watch the units!)

4. Gas Constant “R”

7. A child’s lungs can hold 2.20 L. How many grams of air does the child’s lungs hold at a pressure of 102 kPa and a body temperature of 37 o C? Use a molar mass of 29 g for air, which is about 20% O 2 (32 g/mol) and 80% N 2 (28 g/mol). We must solve for the moles “n” of air in the lungs. Use: PV=nRT P = 102 kPa V = 2.2L n = unknown R = 8.31(kPa·L)/(K·mol) T = 37 o C + 273 = 310 K 102kPa x 2.2L = n x 8.31(kPa·L)/(K·mol) x 310 K n =.087mol grams of air = 0.087 mol x (29 g/mol) = 2.5 g of air

8. Ideal Gases and Real Gases  Ideal Gas works at all temperature, volumes & pressures works at all temperature, volumes & pressures has to conform to assumptions of kinetic theory has to conform to assumptions of kinetic theory no volume & no attraction between the particles no volume & no attraction between the particles  Real Gas particles have volume particles have volume particles are attracted to each other particles are attracted to each other particles can condense or solidify particles can condense or solidify

9. Key Idea Real gases differ most from ideal gas at low temperature and high pressure.

10. Intermolecular attractions dominate when the line is below PV=nRT and volume dominates when the line is above PV=nRT.

11. 1.An aerosol spray can with a volume of 325 mL contains 3.00 g of propane (C 3 H 8 ) as a propellant. What is the pressure in kPa of the gas in the can at 28°C? a. 525 kPa b. 2.31 x 10 4 kPa c. 475 kPa d. 0.525 kPa

12. 1.An aerosol spray can with a volume of 325 mL contains 3.00 g of propane (C 3 H 8 ) as a propellant. What is the pressure in kPa of the gas in the can at 28°C? a. 525 kPa b. 2.31 x 10 4 kPa c. 475 kPa d. 0.525 kPa

13. 2.Find the volume of a gas in liters if 2.95 mol has a pressure of 77.0 kPa at a temperature of 52°C. a.22.4 L b.16.6 L c.103 L d.50.2 L

14. 2.Find the volume of a gas in liters if 2.95 mol has a pressure of 77.0 kPa at a temperature of 52°C. a.22.4 L b.16.6 L c.103 L d.50.2 L

15. 3.An ideal gas differs from a real gas in that the molecules of an ideal gas a.have no attraction for one another. b.have a significant volume. c.have a molar mass of zero. d.have no kinetic energy.

16. 3.An ideal gas differs from a real gas in that the molecules of an ideal gas a.have no attraction for one another. b.have a significant volume. c.have a molar mass of zero. d.have no kinetic energy.