Unit 9 Gases Gases have no definite shape

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Unit 9 Gases

Unit 9 Gases

Gases have no definite shape or volume. Eleven elements are gases at room temperature

Gases have no definite shape or volume. Eleven elements are gases at room temperature and pressure. (color on periodic table on wall? ) Gases turn into liquids or solids at low temperatures and high pressures. Oxygen becomes liquid at -297. 3 o. F or -182. 9 o. C, Nitrogen at -320. 4 o. F or -195. 8 o. C. Air is a mixture of: 78% N 2 21% O 2 1 % Ar 0. 035 % CO 2 + other gases

Units in gases Pressure 1 Atmosphere = 760 mm of Hg = 760 Torr

Units in gases Pressure 1 Atmosphere = 760 mm of Hg = 760 Torr = 14. 7 psi Volume 1 liter = 1000 m. L Temperature All formulas dealing with gases require the use of Kelvin = 273 + o C Absolute Zero is the lowest temperature possible. All motion stops and volume becomes zero at absolute zero. STP = standard temperature (0 o. C) and pressure (1 atm)

Boyles Law P 1 V 1 = P 2 V 2 P 1 =

Boyles Law P 1 V 1 = P 2 V 2 P 1 = initial pressure V 1 = initial volume P 2 = final pressure V 2 = final volume Remember: Pressure can be in atm or mm of Hg Volume can be in liters or m. L A gas at a pressure of 10 atm and a volume of 500 m. L is compressed to a pressure of 100 atm. What is the new volume?

Pressure – Temperature Law P 1 T 1 = P 2 T 2 P

Pressure – Temperature Law P 1 T 1 = P 2 T 2 P 1 = initial pressure T 1 = initial temperature P 2 = final pressure T 2 = final temperature Remember: Pressure can be in atm or mm of Hg Temperature must be in Kelvin A tire has a pressure of 2 atm at 10 o C. What would the pressure be at 30 o C?

Charles Law V 1 T 1 = V 2 T 2 V 1 =

Charles Law V 1 T 1 = V 2 T 2 V 1 = initial volume T 1 = initial temperature V 2 = final volume T 2 = final temperature Remember: Volume can be in liters or m. L Temperature must be in Kelvin A balloon has a volume of 100 m. L at a temperature of 23 o. C. What will its volume be at 70 o. C?

Avogadro’s Law V 1 N 1 = V 2 N 2 V 1 =

Avogadro’s Law V 1 N 1 = V 2 N 2 V 1 = initial volume N 1 = initial number of moles V 2 = final volume N 2 = final number of moles Remember: Volume can be in liters or m. L

General Gas Law This is a combination of the simple gas laws. P 1

General Gas Law This is a combination of the simple gas laws. P 1 V 1 T 1 N 1 = P 2 V 2 T 2 N 2

One mole of any gas: occupies 22, 400 m. L ( or 22. 4

One mole of any gas: occupies 22, 400 m. L ( or 22. 4 liters) at STP occupies 24, 500 m. L (or 24. 5 liters) at 25 o. C and 1 atm. Remember Avogadro’s Law: Equal volumes of gas measured at the same temperature and pressure contain the same number of particles (atoms or molecules).

Ideal Gas Law P V = n R T P = pressure in atm

Ideal Gas Law P V = n R T P = pressure in atm V = volume in liters n = number of moles R = Gas constant 0. 082 liter – atm/mole K T = Kelvin The CO 2 gas cylinder, how many moles of CO 2 can it hold if volume is 15 liters, pressure is 100 atm, and temperature is 20 o. C? How many grams of CO 2 is this number of moles?

A gas at a temperature of 98 o. C occupies 1 liter at a

A gas at a temperature of 98 o. C occupies 1 liter at a pressure of 0. 974 atm. It weighs 2 grams. What is the number of moles of gas? What is the molar mass of the gas?

Dalton’s Law of Partial Pressures – For a mixture of gases, in a container,

Dalton’s Law of Partial Pressures – For a mixture of gases, in a container, the total pressure exerted is the sum of the pressures that each gas would exert if it were alone. PT = P 1 + P 2 + P 3. . .

Kinetic Theory of Molecular Motion n A gas is composed of a large number

Kinetic Theory of Molecular Motion n A gas is composed of a large number of extremely small particles, atoms or molecules. n The total volume of the gas is negligible compared to the volume of the gas. It is mostly empty space n The particles are in constant, random, straight – line motion. When the gas particles collide with the walls of the container, pressure is exerted. Collisions are elastic, particles have the same Kinetic energy before and after collisions. n There are no forces of attraction between the gas particles. n The average Kinetic energy of the gas is directly proportional to the temperature of the gas.

Review 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 1. 2. 3.

Review 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 1. 2. 3. 4. i n f o j s a k b p Molecules Great, empty Volume Motion 11. t 12. g 13. q 14. d 15. c 16. m 17. e 18. h 19. l 20. r 5. 6. 7. 8. Elastic, kinetic collisions kinetic attraction

Chem Mystery Word Puzzle (on gases) 1. Adiabatic 3. Baro 5. Butane 6. Cath

Chem Mystery Word Puzzle (on gases) 1. Adiabatic 3. Baro 5. Butane 6. Cath 9. Compressibility 11. Critical 15. Graham 18. iso 21. liquefaction 23. mano 30. 31. 35. 36. 41. octet partial real size Van der Waals