1. Ch. 10 Gases

2. Characteristics of Gases b Gases expand to fill any container. random motion, no attraction b Gases are fluids (like liquids). no attraction b Gases have very low densities. no volume = lots of empty space

3. Characteristics of Gases b Gases can be compressed. no volume = lots of empty space b Gases undergo diffusion & effusion. random motion

4. Kinetic Molecular Theory b Model used to predict behavior of a gas on a molecular level Assumes gas is an ideal gas b Ideal gas- a model that effectively describes the behavior of a real gases at conditions close to standard temperature and pressure

5. Kinetic Molecular Theory b Particles in an ideal gas… have no volume. have elastic collisions. are in constant, random, straight- line motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin temperature. DO NOT EXIST!!!

6. Real Gases b Particles in a REAL gas… have their own volume attract each other b Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

7. TemperatureTemperature ºF ºC K -45932212 -2730100 0273373 K = ºC +273.16 b Always use absolute temperature (Kelvin) when working with gases.

8. PressurePressure Which shoes create the most pressure?

9. PressurePressure Total force exerted by the moving particles of a gas as they collide with the walls of a container

10. PressurePressure b Barometer measures atmospheric pressure Mercury Barometer Aneroid Barometer

11. PressurePressure b Manometer measures contained gas pressure U-tube ManometerBourdon-tube gauge

12. PressurePressure b KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

13. STPSTP Standard Temperature & Pressure 0°C 273.16 K 1 atm101.325 kPa -OR- STP

14. STPSTP Standard Temperature & Pressure 1 mole of a gas at STP = molar volume 1 molar volume of any gas is 22.4 L 1 mole of any gas = 22.4 L STP

15. A. Boyle’s Law b The pressure and volume of a gas are inversely related at constant mass & temp P V P 1 V 1 = P 2 V 2

16. V T Charles’ Law b The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure

17. Combined Gas Law P1V1T1P1V1T1 = P2V2T2P2V2T2

18. GIVEN: V 1 = 473 cm 3 T 1 = 36°C = 309.16K V 2 = ? T 2 = 94°C = 367.16K WORK: V 1 /T 1 = V 2 /T 2 Gas Law Problems b A gas occupies 473 cm 3 at 36°C. Find its volume at 94°C. CHARLES’ LAW TT VV (473 cm 3 )(367 K)=V 2 (309 K) V 2 = 560 cm 3

19. GIVEN: V 1 = 100. mL P 1 = 150. kPa V 2 = ? P 2 = 200. kPa WORK: P 1 V 1 = P 2 V 2 Gas Law Problems b A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa. BOYLE’S LAW PP VV (150.kPa)(100.mL)=(200.kPa)V 2 V 2 = 75.0 mL

20. GIVEN: V 1 = 7.84 cm 3 P 1 = 71.8 kPa T 1 = 25°C = 298 K V2 = ?V2 = ? P 2 = 101.325 kPa T 2 = 273 K WORK: P 1 V 1 /T 1 = P 2 V 2 /T 2 (71.8 kPa)(7.84 cm 3 )(273 K) =(101.325 kPa) V 2 (298 K) V 2 = 5.1 cm 3 E. Gas Law Problems b A gas occupies 7.84 cm 3 at 71.8 kPa & 25°C. Find its volume at STP. P  T  VV COMBINED GAS LAW