Charles Law

At higher temperatures, the particles in a gas have greater kinetic energy. The volume of a gas is directly proportional to temperature when the pressure (P) and number of moles (n) are constant. T V T V To be an accurate direct proportion, the line must go through the origin volume temperature V1 = V2 T1 T2

New Temperature Scale Kelvin K = °C + 273 This new scale allows a direct proportion and no need for negative temperature values MUST USE FOR ALL GAS LAWS!! Standard temperature

Absolute zero Zero kelvin Lowest temperature possible All molecule motion stops Never been achieved

Ex. A sample of helium occupies 473 cm3 at 36°C Ex. A sample of helium occupies 473 cm3 at 36°C. What will be the volume when temperature is increased to 94°C? V1= 473 cm3 T1 = 36 + 273 = 309 K V2 = ? T2 = 94 + 273 = 367 K V1 = V2 T1 T2 V2 (473 cm3) = (309 K) (367 K) (473 cm3)(367 K) = (309 K)V2 V2 = 562 cm3 (309 K) (309 K)

Combined Gas Law

Put Boyle’s and Charles’ Law together to make the Combined Gas Law P1V1 = P2V2 T1 T2

Ex. A gas has a volume of 7. 84 mL at 71. 8 kPa and 25. 0°C Ex. A gas has a volume of 7.84 mL at 71.8 kPa and 25.0°C. What will be the volume at STP? P1 = 71.8 kPa V1 = 7.84 mL T1 = 25 + 273 = 298 K P2 = 101.325 kPa V2 = ? T2 = 0 + 273 = 273 K P1V1 = P2V2 T1 T2 (71.8 kPa)(7.84 mL) = (101.325 kPa)V2 298 K 273 K (71.8 kPa)(7.84 mL)(273 K) = (101.325 kPa)(273 K)V2 (101.325 kPa)(298 K) (101.325 kPa)(273 K) V2 = 5.09 mL