Gases
Temperature Always use the Kelvin scale when working with gases. ºC K -273 100 273 373 K = ºC + 273
Practice 23.5°C = __________K 296.5 K -15.4°C = _________ K 257.6 K
E. Pressure Which shoes create the most pressure?
E. Pressure Barometer measures atmospheric pressure Aneroid Barometer Mercury Barometer Aneroid Barometer
E. Pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi
Standard Temperature & Pressure F. STP STP Standard Temperature & Pressure 0°C 273 K 1 atm 101.325 kPa -OR-
Pressure Conversions Convert each of the following into mm Hg 1.25 atm 2.48 x 10-3 atm 4.75 x 104 atm
Answers 950. mm Hg 1.88 mm Hg 3.61 x 107 mm Hg
Pressure Conversions Convert 109 kPa to atm Convert 0.62 atm to mm Hg Convert 0.3587 atm to kPa Convert 29.32 mmHg to kPa
Answers 1.08 atm 470 mm Hg 36.345 kPa 3.91 kPa
Gases II. The Gas Laws P V T
Can you Explain the Following? When deep sea fish rise through the water too quickly, their internal organs may be pushed out through their mouths. Tire pressure decreases in colder weather A balloon deflates in cold weather
Gas Law Animation http://www.youtube.com/watch?v=eYeRA--Xq0E
Boyle’s Law A. Pressure vs. Volume The pressure and volume of a gas are inversely related This means that when pressure increases, volume decreases and vice versa! P V
http://www.youtube.com/watch?v=bWhs5L_gBTI
Charles’ Law B. Temperature vs. Volume The volume and temperature (K) of a gas are directly related When temperature increases, volume increases V T
http://www.youtube.com/watch?v=Cr7xGEI0KDc
Gay-Lussac’s Law C. Pressure vs. Temperature The pressure and temperature (K) of a gas are directly related When temp. increases, pressure increases P T
Combined Gas Law P1V1 T1 = P2V2 T2 P1V1T2 = P2V2T1
E. Gas Law Problems A gas occupies 473 cm3 at 36°C. Find its volume at 94°C. GIVEN: V1 = 473 cm3 T1 = 36°C = 309K V2 = ? T2 = 94°C = 367K T V WORK: P1V1T2 = P2V2T1 (473 cm3)(367 K)=V2(309 K) V2 = 562 cm3
E. Gas Law Problems A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa. GIVEN: V1 = 100. mL P1 = 150. kPa V2 = ? P2 = 200. kPa P V WORK: P1V1T2 = P2V2T1 (150.kPa)(100.mL)=(200.kPa)V2 V2 = 75.0 mL
E. Gas Law Problems P T V V1 = 7.84 cm3 P1 = 71.8 kPa A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP. GIVEN: V1 = 7.84 cm3 P1 = 71.8 kPa T1 = 25°C = 298 K V2 = ? P2 = 101.325 kPa T2 = 273 K P T V WORK: P1V1T2 = P2V2T1 (71.8 kPa)(7.84 cm3)(273 K) =(101.325 kPa) V2 (298 K) V2 = 5.09 cm3
E. Gas Law Problems A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr? GIVEN: P1 = 765 torr T1 = 23°C = 296K P2 = 560. torr T2 = ? P T WORK: P1V1T2 = P2V2T1 (765 torr)T2 = (560. torr)(296K) T2 = 217 K = -56°C