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Understanding Gas Laws: Characteristics, Principles, and Applications

Learn about the physical properties of gases, the ideal gas law, and key gas laws such as Boyle's Law and Charles' Law. Explore pressure, temperature relationships, and solve gas law problems with this comprehensive guide.

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Understanding Gas Laws: Characteristics, Principles, and Applications

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  1. Ch. 11 - Gases I. Physical Properties

  2. A. Kinetic Molecular Theory • 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.

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

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

  5. C. Characteristics of Gases • Gases can be compressed. • no volume = lots of empty space • Gases undergo diffusion & effusion. • random motion

  6. D. Temperature K = ºC + 273 ºF -459 32 212 ºC -273 0 100 K 0 273 373 • Always use absolute temperature (Kelvin) when working with gases.

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

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

  9. E. Pressure U-tube Manometer Bourdon-tube gauge • Manometer • measures contained gas pressure

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

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

  12. V T P Ch. 11 - Gases II. The Gas Laws

  13. A. Boyle’s Law P V • The pressure and volume of a gas are inversely related • at constant mass & temp PV = k

  14. A. Boyle’s Law

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

  16. B. Charles’ Law

  17. C. Gay-Lussac’s Law P T • The pressure and absolute temperature (K) of a gas are directly related • at constant mass & volume

  18. D. Combined Gas Law P1V1 T1 P2V2 T2 = P T V T PV T PV = k P1V1T2 =P2V2T1

  19. E. Gas Law Problems • A gas occupies 473 cm3 at 36°C. Find its volume at 94°C. CHARLES’ LAW 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

  20. E. Gas Law Problems • A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa. BOYLE’S LAW 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

  21. E. Gas Law Problems • A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP. COMBINED GAS LAW 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

  22. E. Gas Law Problems • A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr? GAY-LUSSAC’S LAW 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

  23. END OF QUIZ I MATERIAL

  24. Ch. 11 - Gases III. Ideal Gas Law

  25. A. Avogadro’s Principle V n • Equal volumes of gases contain equal numbers of moles • at constant temp & pressure • true for any gas

  26. A. Ideal Gas Law p. 384 = k V n Merge the Combined Gas Law with Avogadro’s Principle: PV T PV nT = R UNIVERSALAS CONSTANT R=0.0821 Latm/molK R = 62.4 Lmm Hg/molK (torr) R=8.315 dm3kPa/molK You don’t need to memorize these values!

  27. A. Ideal Gas Law PV=nRT UNIVERSAL GAS CONSTANT R=0.0821 Latm/molK R = 62.4 Lmm Hg/molK (torr) R=8.315 dm3kPa/molK You don’t need to memorize these values!

  28. C. Ideal Gas Law Problems • Calculate the pressure in atmospheres of 0.412 mol of He at 16°C & occupying 3.25 L. GIVEN: P = ? atm n = 0.412 mol T = 16°C = 289 K V = 3.25 L R = 0.0821Latm/molK WORK: PV = nRT P(3.25)=(0.412)(0.0821)(289) L mol Latm/molK K P = 3.01 atm

  29. C. Ideal Gas Law Problems WORK: 85 g 1 mol = 2.7 mol 32.00 g • Find the volume of 85 g of O2 at 25°C and 104.5 kPa. GIVEN: V=? m=85 g T=25°C = 298 K P=104.5 kPa R=8.315dm3kPa/molK n= 2.7 mol PV = nRT (104.5)V=(2.7) (8.315) (298) kPa mol dm3kPa/molKK V = 64 dm3

  30. Let’s Practice!! Handout p.24 Things to remember: • OMIT 5 & 6 • Convert temperatures to Kelvin (add 273) • Convert all volumes to Liters (mL to L  divide by 1000) • Use R value that matches pressure unit

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