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Gas Laws

Gas Laws . Chapter 14. Kinetic Molecular Theory of Gases. No attraction/repulsion Volume of particles is 0 Constant motion Elastic collisions Temperature equals the average kinetic energy of all particles. Factors Affecting Gas Pressure. Amount of Gas (n=moles) Volume (Liters)

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Gas Laws

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  1. Gas Laws Chapter 14

  2. Kinetic Molecular Theory of Gases • No attraction/repulsion • Volume of particles is 0 • Constant motion • Elastic collisions • Temperature equals the average kinetic energy of all particles

  3. Factors Affecting Gas Pressure • Amount of Gas (n=moles) • Volume (Liters) • Temperature (Kelvin) 1atm = 760 mm Hg = 760 Torr = 101.3 kPa = 14.7 psi Remember: K=oC +273

  4. Boyle’s Law • At constant temperature, pressure and volume are inversely related. • P1V1 = P2V2

  5. Practice: Boyle’s Law A gas system has an initial volume of 2.36L with the pressure unknown. When the volume changes to 2290mL the pressure is found to be 6390torr What was the initial pressure in atm?

  6. Charles’s Law • At constant pressure, volume and temperature are directly related. • V1/T1 = V2/T2

  7. Practice: Charles’s Law Calculate the final temperature of a gas in Celsius when 2L of the gas at 128K is compressed to 0.5L?

  8. What About Pressure and Temperature? Gay Lussac’s Law • At constant volume, pressure and temperature are directly related • P1/T1 = P2/T2

  9. Practice What is the final pressure of a sample of gas that has an initial pressure of 89.3kPa when its temperature is raised from 25oC to 100oC?

  10. Combined Gas Law • P1V1/n1T1 = P2V2/n2T2 http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/gasesv6.swf A closed gas system initially has pressure and temperature of 1.56atm and 629K with the volume unknown. If the same closed system has values of 195torr, 9940mL and 523K, what was the initial volume in L?

  11. ASSIGNMENT • Practice Problems (Section 14.2): • # 7-14

  12. IDEAL GAS LAW • PV=nRT • R= 0.0821 L*atm/mol*K = 8.31 L*kPa/mol*K Calculate the pressure in a 212 Liter tank containing 23.3 kg of argon gas at 25°C?

  13. Ideal v. Real Gases • They’re the same except at • EXTREMELY LOW T • EXTREMELY HIGH P

  14. Assignment Section 14.3 Assessment • # 25-30

  15. Ideal Gas Law and Molar Mass • M=mRT/PV given n=m/M Where n=moles, m=mass and M=molar mass • How many grams of gas are present in a sample that has a molar mass of 70 g/mol and occupies a 2.00 L container at 117kPa and 35.1 oC?

  16. Gas Constant (R) • 0.0821 L atm • mole K • 62.4L mm Hg mole K 8.314 L kPa mole K

  17. From Friday • How many moles of gas were in your bottle each time?

  18. Ideal Gas Law and Density • D=MP/RT given n=m/M and D=m/V • What is the density of a gas at STP that has a molar mass of 44.0 g/mol?

  19. Dalton’s Law of Partial Pressure • Pressure and moles of gas are directly proportional. • Ptotal= P1 + P2 + P3 + … • http://www.tlv.com/global/US/steam-theory/steam-partial-pressure-pt1.html

  20. Gas Stoichiometry If 1.39 g of ethane(C2H6) is reacted with oxygen, what volume of carbon dioxide is produced at:  • STP? • 12.3oC at 107.4KPa?

  21. Avogadro’s Principle • Equal volumes of gas at the same temperature and pressure have equal numbers of particles. • Translation: 1 mole = 22.4 L = 6.02 x 1023 gas particles

  22. Diffusion/Effusion • Diffusion- gases move toward areas of lower concentration • Effusion- gas escaping through tiny holes in container

  23. Graham’s Law of Gaseous Effusion

  24. TEST • 30 MC Questions • 5 problems requiring elegant solutions

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