1. Please pick up  a copy of two problem sets Wet Gases problem set Gas Bulb Problems problem set

2. Gaseous Mixtures Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

3. Gaseous Mixtures  Reading Assignment: Zumdahl, Chapter 5.5, 17.4  Gas Mixtures Mole fraction Dalton's Law of Partial Pressures Vapor pressure Wet gases

4. Atmospheric Composition  Dry air 78% N 2, 21% O 2, 1%Ar  Normal air N 2, O 2, Ar, 0.03% CO 2, 1.6% H 2 O

5. Mole Fraction  The ratio of moles of a compound in a mixture to the total moles in the mixture.  A = +++ mol A ABC...  A gas sample contains 3 moles of hydrogen and 2 moles of oxygen. What is the mole fraction of each gas?

6. Mole Fraction  H2H2 = moles H 2 moles H 2 + moles O 2 = 3 3 + 2 = 0.60  O2O2 = moles O 2 moles H 2 + moles O 2 = 2 3 + 2 = 0.40 The sum of the mole fractions in a mixture equals exactly 1

7. Partial Pressure  The pressure a fixed amount of gas would exert if it were alone in a given volume at a given temperature.

8. Gas Bulb 3 liters, 2 atm2 liters, 1 atm What will happen when the stopcock is opened?

9. Gas Bulb 3 liters, 2 atm2 liters, 1 atm What will be the pressure of the orange atoms? Hint: Use Boyle’s Law

10. Gas Bulb 3 liters, 2 atm2 liters, 1 atm P · V = constant 2 atm · 3 L = 6 L· atm P orange · 5 L = 6 L· atm P orange = 1.2 atm Partial pressure

11. Dalton's Law of Partial Pressures  The total pressure of a non-reacting gaseous mixture is the sum of the partial pressures of each gas in the mixture. P total = P A + P B + P C +...

12. Gas Bulb 3 liters, 2 atm2 liters, 1 atm What is the total pressure in the left bulb? 1.6 atm What is the total pressure in the right bulb? 1.6 atm

13. Dalton's Law of Partial Pressures What is the mole fraction of each gas? P A = P total ·  A What is the partial pressure of each gas?

14. Vapor Pressure  The pressure exerted by the vapor of a substance when in equilibrium with the substance. Even below their boiling point, liquids evaporate or vaporize and solids sublime.

15. Vapor Pressure If a container is closed, then only a certain amount of liquid will evaporate until the air is saturated with the vapor. Adding additional liquid does not increase the amount of vapor in the air.

16. Vapor Pressure Boiling occurs when the vapor pressure of a liquid equals or exceeds the restraining pressure (e.g., atmospheric pressure) Is it possible for water to boil at room temperature?

17. Vapor Pressure of Water 0 20 40 60 80 100 01020304050 Temperature ( ° C) Pressure (torr) Increases non-linearly with increasing temperature.

18. Wet Gases Gases trapped by liquid displacement. PPP totalgaswater vapor =+ Is the pressure of the trapped gas equal to, less than or greater than atmospheric pressure?

20. Common Gases Room Temperature, One Atmosphere Pressure  Monatomic: He, Ne, Ar, Kr, Xe, Rn  Polyatomic Elements: H 2, N 2, O 2, O 3, F 2, Cl 2 Compounds: CO, CO 2, NO, N 2 O, NO 2, N 2 O 4, N 2 O 5, CH 4, C 2 H 6, C 2 F 4, etc.