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Gases

Learn about gas laws such as Boyle's Law, Charles' Law, Gay-Lussac's Law, and the Combined Gas Law. Also, understand how to convert pressure measurements between different units.

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Gases

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  1. Gases

  2. Temperature K = ºC + 273 ºC -273 0 100 K 0 273 373 • Always use the Kelvin scale when working with gases.

  3. Practice • 23.5°C = __________K 296.5 K • -15.4°C = _________ K 257.6 K • 325.85 K = ________ °C • 52.85 °C • 96.2 K = _________ °C • -176.8 °C

  4. E. Pressure Which shoes create the most pressure?

  5. E. Pressure Aneroid Barometer Mercury Barometer • Barometer • measures atmospheric pressure

  6. E. Pressure • KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

  7. F. STP Standard Temperature & Pressure 0°C273 K 1 atm101.325 kPa -OR- STP

  8. Pressure Conversions • Convert each of the following into mm Hg • 1.25 atm • 2.48 x 10-3 atm • 4.75 x 104 atm

  9. Answers • 950. mm Hg • 1.88 mm Hg • 3.61 x 107 mm Hg

  10. 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

  11. Answers • 1.08 atm • 470 mm Hg • 36.345 kPa • 3.91 kPa

  12. V T P Gases II. The Gas Laws

  13. 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

  14. Gas Law Animation • http://www.youtube.com/watch?v=eYeRA--Xq0E

  15. Boyle’s Law P V 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!

  16. http://www.youtube.com/watch?v=bWhs5L_gBTI

  17. Charles’ Law V T B. Temperature vs. Volume • The volume and temperature (K) of a gas are directly related • When temperature increases, volume increases

  18. http://www.youtube.com/watch?v=Cr7xGEI0KDc

  19. Gay-Lussac’s Law P T C. Pressure vs. Temperature • The pressure and temperature (K) of a gas are directly related • When temp. increases, pressure increases

  20. Combined Gas Law P1V1 T1 P2V2 T2 = P1V1T2 =P2V2T1

  21. 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

  22. 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

  23. E. Gas Law Problems • A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP. P T V GIVEN: V1=7.84 cm3 P1=71.8 kPa T1=25°C = 298 K V2=? P2=101.325 kPa T2=273 K WORK: P1V1T2 = P2V2T1 (71.8 kPa)(7.84 cm3)(273 K) =(101.325 kPa)V2 (298 K) V2 = 5.09 cm3

  24. 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

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