1. CHM 108 SUROVIEC SPRING 2014 Chapter 5 1

2. I. Pressure A. Molecular collisions Pressure = Force Area (force = mass x acceleration) 2

3. I. Pressure B. Pressure Units Barometer 3

4. II. Gas Laws A sample of gas has 4 physical properties that are interrelated. 4

5. A. Boyle’s Law Relationship between pressure and volume at constant T and n. 5

6. A. Boyle’s Law If you were to go SCUBA diving, your lunch capacity is a constant. So if you moved from the bottom at 3 atm to the surface at 1 atm with out breathing, what happens to the volume of the air in your lungs? 6

7. B. Charles’ Law At constant pressure and moles, volume decreases with decreasing temperature. 7

8. B. Charles’ Law Given a balloon that has 3.20L to start off at room temperature (25 o C) and is submerged into liquid N 2 the volume shrinks down to 0.816L what is the temperature of liquid N 2 ? 8

9. C. Avogadro’s Law Relationship between volume and number of moles and constant T and P 9

10. C. Avogadro’s Law A 3.86 L container contains 0.252 moles of gas. How many moles of the same gas would be required to fill a 8.50L container? 10

11. II. Ideal gas law Knowing each of these individual gas laws allows us to make a law that covers all ideal gas situations. 11

12. II. Ideal gas law 1. What is the volume of 8.24 g of CO 2 (g) at STP? 2. Argon light bulbs have a pressure of 1.20 atm and are at a temperature of 18 o C. When they are turned on they heat to a temperature of 85 o C. What is the new pressure at this temperature? 12

13. III. Using the ideal gas law A. Density  One mole of an ideal gas occupies 22.4L  Density of a gas is directly proportional to molar mass 13

14. A. Density Determine the M and molecular formula of an unknown compound that contains Fe and O 14

15. B. Gas stoichiometry Stoichiometry for gas reactions is the same if it were a liquid or a solid. Use the balanced chemical equation. Amount of reactant  moles of reactant  moles of product  amount of product What is the volume of CO 2 produced at 37 o C and 1.00atm when 5.60g of glucose is reacted in the following reaction: C 6 H 12 O 6 (s) + 6O 2 (g)  6CO 2 (g) + 6H 2 O(l) 15

16. III. Mixture of Gases & Partial Pressure Partial pressure = Pressure of individual gas components in a mixture Dalton’s Law = total pressure of a mixture of gasses is just sum of the pressure each gas would exert individually Mole fraction = dimensionless quantity that expresses the ratio of the number of moles in 1 component to the number of moles in all the components 16

17. A. Partial Pressures V and T are constant P1P1 P2P2 P total = P 1 + P 2 17

18. A. Partial Pressures Knowing: P total = P 1 + P 2 PV = nRT 18

19. A. Partial Pressures A sample of natural gas contains 8.24 moles of CH 4, 0.421 moles of C 2 H 6, and 0.116 moles of C 3 H 8. If the total pressure of the gases is 1.37 atm, what is the partial pressure of propane (C 3 H 8 )? 19

20. IV. Kinetic molecular Theory Gas laws help predict behaviors of gasses, but they do not explain what is happening at the molecular level. We know that hot air rises and can predict the results (Charles’ Law), but why does it do that? 20

21. A. Kinetic Molecular Theory 1.A gas is composed of molecules that are separated from each other by distances far greater than their own dimensions. The molecules can be considered to be points; that is, they possess mass but have negligible volume. 2.Gas molecules are in constant motion in random directions, and they frequently collide with one another. Collisions among molecules are perfectly elastic. 1.Gas molecules exert neither attractive nor repulsive forces on one another. 4.The average kinetic energy of the molecules is proportional to the temperature of the gas in Kelvins. Any two gases at the same temperature will have the same average kinetic energy 21

22. B. Velocity of gases Using what we know of the gas laws and using these postulates we can see why gases behave the way they do. 22 KE= ½ mu 2

23. B. Velocity of gases 23 The distribution of speeds of three different gases at the same temperature

24. B. Temperature effects Average kinetic energy is proportional to temperature. 24

25. B. Temperature effects 25 The distribution of speeds for nitrogen gas molecules at three different temperatures

26. B. Using the Kinetic Molecular Theory Calculate the u rms for O 2 and Ar at 298K. Which has the faster moving gas molecules? 26