Properties of Gases and Gas Laws

1. Properties of Gases and Gas Laws Ch. 14.1 & 14.2

2. Properties of Gases • Gases are easily compressed • Gases can expand • Large amount of space between particles

3. Properties of Gases • Compressing a gas causes pressure to increase • 3 Factors Affect Gas Pressure • Volume of the container (V) • Measured in Liters • Amount of gas (n) • Measured in the number of moles • Temperature • Measured in Kelvins (T)

4. Properties of Gases • Amount of gas affects on pressure • Increase in number of particle • Increases in number of collisions • Increase in Pressure • As the amount of gas changes, the pressure changes directly • Ex. When the number of moles is doubled the pressure double. • Also works when the moles decreases

5. Properties of Gases • Gases will flow to the area with lower pressure. • Ex: • Deflating balloon • Gas will leave the balloon into the surroundings • Vacuum sealed container • Gas will rush into the container

6. Properties of Gases • Volume’s effects on pressure • Decrease in volume of the container • Increase in the number of collisions • Increase in pressure • Volume inversely affects pressure • A volume decrease causes a pressure increase • If the volume is halved, the pressure is doubled. • Squeezing a pack of Ketchup

7. Properties of Gases • Temperature’s affects on pressure • Increase in Temperature • Increase in the speed of the gas particles • Increase in the number of collisions • Increase in pressure • Temperature directly affects pressure • If the temperature double, so will the pressure • Ex: Frozen balloon

8. The Gas Laws • Boyle’s Law • For a given mass of gas at constant temperature, the volume of a gas varies inversely with pressure.

9. The Gas Laws • Boyle’s Law • P₁×V₁=P₂×V₂ • Pressure in units of kilopascals (kPa) • Volume in units of liters (L)

10. The Gas Laws • Boyle’s Law Ex: • The volume of a raft has an initial volume of 1.2 liters and an initial pressure of 87kPa. If the final volume was 2.9 liters what was the final pressure? • P₁=87kPa V₁=1.2L P₂=? V₂=2.9 • P₁×V₁=P₂×V₂ (P₁×V₁)/ V₂ =P₂ • (87x1.2)/2.9= 36 kPa

11. The Gas Laws • Charles Law: As the temperature of an enclosed gas increases, the volume increases, if the pressure is constant.

12. The Gas Laws • Charles Law: • V₁/T₁=V₂/T₂ • Volume in units of Liters (L) • Temperature in units of Kelvins (K)

13. The Gas Laws • Charles Law Ex: • The volume of an inflated balloon at 24˚C has a volume of 4 liters. The balloon is then moved to a room with a temperature of 58˚C. What is the Volume? • T₁= 24˚C+ 273 = 292 K T₂= 58˚C + 273 = 331 K • V₁/T₁=V₂/T₂ V₂ = (V₁xT₂)/ T₁ • (4.00L x 331 K)/ 297 K= 4.46L

14. The Gas Laws • Gay-Lussac’s Law • As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant. • P₁/T₁=P₂/T₂ • Pressure: kPa • Temperature: K

15. The Gas Laws • Gay-Lussac’s Law Ex: • An aerosol can is stored at 25˚C and has a pressure of 103 kPa. If the f=can is heated to 928˚C, what is the final pressure? • T₁=25˚C + 273= 298 K • T₂= 928˚C + 273= 1201 K • P₁/T₁=P₂/T₂ T₂(P₁/T₁)=P₂ • 103kPa x (1201 K / 298 K)= 415 kPa • Or 4.15 x 10² kPa

16. The Gas Laws • The Combined Gas Law • Calculates for situations where the amount of gas is constant. • (P₁ x V₁)/T₁= (P₂ x V₂)/ T₂ • P: kPa • V: L • T: K

17. The Gas Laws • Combined Gas Law Ex: • The volume of a balloon is 30.0 L at 313 K and 153 kPa pressure. What would the volume be at standard temperature and pressure (STP) • STP: 273K and 101.3 kPa • (P₁ x V₁)/T₁= (P₂ x V₂)/ T₂ • V₂= (V₁ x P₁ x T₂)/ (P₂ x T₁) • (30L x 53kPa x 273K)/(101.3kPa x 313K)= 39.5 L

18. #1 • Gas law

19. Ideal Gas Law 14.3

20. Ideal Gas Law • Ideal Gas Law was created to calculate the number of moles of a contained gas. • Symbol for number of moles is “n” • Number of moles is directly proportional to volume

21. Ideal Gas Law • 1mol of every gas is 22.4 L at STP • The Ideal Gas Constant R=(P x V)/(T x n) • At STP : • (101.3 x 22.4)/(273 x 1)= 8.31(L·kPa)/(K·mol) • R= 8.31

22. Ideal Gas Law • Common Equation • PV= nRT • P: kPa • V: L • n: mol • R: (L·kPa)/(K·mol) • T: K

23. Review • Converting mass to moles. • 12 grams of CO₂ how many moles? • 12grams/(MMof C + 2 x the MMof O) • 12/(12+2·16)= .2727 mols

24. Ex. • What is the pressure of 113g of Xenon gas at 187˚C, held in a 1.2L container? • nRT/V=P • 113g/131.3MM of Xe= .8606 mols • T= 187˚C+ 273= 460k • (.8606·8.31·460)/1.2= 2741.44 kPa

25. Gases, Part 3

26. Real Gases vs. Ideal Gases: • Ideal gases follow the gas laws at all pressures and temperatures. • Real gases can not be described by the gas laws at certain temps or pressures.

27. An ideal gas has particles with NO volume, and there are no attractions between the particles.

29. A real gas has particles that have volume, and there are interactions between particles. • Real gases differ most from ideal gases at high pressures and low temperatures.

32. Partial pressure: The pressure that one gas contributes to the total pressure. • Dalton’s Law: Ptotal = P1 + P2 + P3 + …

34. 101.3 kPa

35. On top of Mt. Everest, air pressure is 33.73 kPa. Since oxygen is 21% of air, the pressure of oxygen is 7 kPa. You need 10.67 kPa Oxygen to live, so must Have compressed O2.

36. Diffusion: The tendency of molecules to spread out evenly. • Effusion: A gas escapes through a tiny hole. • Lower the molar mass of a gas = Faster Effusion and Diffusion.

38. Graham’s Law: RateA / Rate B = (Molar mass B / Molar mass A)^.5