1. The Gas Laws The Behavior of Gases

2. The Combined Gas Law The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.

3. A. Boyle’s Law P 1 V 1 = P 2 V 2

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

5. B. Charles’ Law

6. The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure Temperature MUST be in Kelvin

7. C. Gay-Lussac’s Law

8. The pressure and absolute temperature (K) of a gas are directly related at constant mass & volume Temperature MUST be in Kelvin

9. PV PTPT VTVT T D. Combined Gas Law P1V1T1P1V1T1 = P2V2T2P2V2T2 P 1 V 1 T 2 = P 2 V 2 T 1

10. GIVEN: V 1 = 473 cm 3 T 1 = 36°C = 309K V 2 = ? T 2 = 94°C = 367K WORK: Gas Law Problems A gas occupies 473 cm 3 at 36°C and 1 atm. Find its volume at 94°C and 1 atm. CHARLES’ LAW TT VV (473 cm 3 )(367 K)=V 2 (309 K) V 2 = 562 cm 3

11. GIVEN: V 1 = 100. mL P 1 = 150. kPa V 2 = ? P 2 = 200. kPa WORK: Gas Law Problems A gas occupies 100. mL at 150. kPa and 25°C. Find its volume at 200. kPa and 25°C. BOYLE’S LAW PP VV (150.kPa)(100.mL)=(200.kPa)V 2 V 2 = 75.0 mL

12. 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: (71.8 kPa)(7.84 cm 3 )(273 K) =(101.325 kPa) V 2 (298 K) V 2 = 5.09 cm 3 Gas Law Problems 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

13. GIVEN: P 1 = 765 torr T 1 = 23°C = 296K P 2 = 560. torr T 2 = ? WORK: Gas Law Problems The pressure of a gas in a 25.0L tank is 765 torr at 23°C. At what temperature will the pressure be 560. torr? GAY-LUSSAC’S LAW PP TT (765 torr)T 2 = (560. torr)(296K) T 2 = 217 K = -56°C

14. E. Avogadro’s Law The volume and moles of a gas are directly related at constant temperature & pressure

15. GIVEN: V 1 = 36.7 L n 1 = 1.5 mol V 2 = 16.5 L n 2 = ? WORK: Gas Law Problems Consider 2 samples of N 2. Sample 1 contains 1.5 mol N 2 with a volume of 36.7 L at 25°C and 1 atm. Sample 2 has a volume of 16.5 L at 25°C and 1 atm. How many moles of N2 are in Sample 2? AVOGADRO’S LAW VV nn n 2 = 0.67 mol