2. Nature of Gases 1 – gases have mass (low density) 2 – particles glide past one another (flow) - fluid 3 – easily compressed 4 – fill containers completely 5 – diffuse easily* 6 – gases exert pressure 7 – pressure depends on temperature *diffusion – spontaneous mixing of the particles of two substances -movement of one substance through another

3. Kinetic Theory Explains properties of gases (ideal gas) 1. Gas particles are relatively far apart 2. Collisions are elastic 3. Gas particles are in constant, fast, random motion (Brownian motion) 4. Gas particles do not stick, like billiard balls 5. Kinetic energy depends on temperature

4. Pressure force per unit area pressure = force/area SI unit of force – newton (N) STP – standard temperature and pressure ◦ 1 atm and 0 ° C

5. Units of Pressure Unit of PressureStandard atmosphere1 atm millimeters of mercury760 mm Hg torr760 torr inches mercury29.9 in pounds per square inch14.7 psi bar 1 bar = 100 kPa kilopascals101.3 kPa Conversions: How many atmospheres are equal to 10 psi? If a pressure is equal to 101.3 kPa, what is the pressure in mm Hg?

6. Types of Pressure atmospheric pressure ◦ pressure exerted by the air pressing down on earths surface ◦ measured by barometer and manometer gas pressure ◦ gas particles colliding with the sides of the container it is in

7. Barometer an instrument that measures atmospheric pressure

8. Manometer an instrument that measures pressure of a gas in a container vacuum

9. THE GAS LAWS

10. Avogadro’s Law equal volumes of gases at the same temperature and pressure have equal numbers of particles 1 mole of any gas = 22.4 L

11. Dalton’s Law of Partial Pressure the sum of the partial pressures of each gas in a mixture equals the total pressure of the mixture P t = P 1 + P 2 + P 3 ….

12. Classwork/Homework In your books (Modern Chemistry) ◦ pg 312  Section Review 1-4  pg 327 16-19  Pg 329 39 Skim Chapter 10 Section 3 for tomorrow

13. Boyle’s Law P 1 V 1 = P 2 V 2 temperature remains constant pressure and volume are inversely related ◦ P – pressure ◦ V – volume ◦ T - temperature

14. Practice Problems At a constant temperature, the volume of a gas is 30.2 L and the pressure is 356 torr. If the pressure has increased to 700. torr, what is the new volume of the gas? At STP, carbon dioxide fills a 6.5 L container. If the container is compressed to a volume of 3.2 L, what pressure (in kPa) will the gas exert?

15. Charles’ Law V 1 = V 2 T 1 T 2 pressure remains constant volume is directly related to temperature temperature must be in K K-273 = C

16. Practice Problems A balloon filled with helium at STP has a volume of 4.7 L. If pressure is held constant and the temperature is raised 10 degrees Celsius, what is the new volume of the balloon? A 500. mL container houses argon at 373 K. If the container is compressed to a new volume of 0.300 L, what will the temperature of the gas be (assuming pressure remains the same)

17. Gay-Lussac’s Law P 1 = P 2 T 1 T 2 volume remains constant pressure is directly related to temperature

18. Practice Problems A container of gas with a temperature of 290 K has a pressure of 1.9 atm. This container is pressurized so the new temperature is 397 K. What is the new pressure? The volume of a fixed container is 4.03 L. It is filled with neon gas at 46 degrees Celsius and the gas exerts a pressure of 800 torr. This container is heated to 84 degrees celcius. What pressure does the gas exert?

19. Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 No variable remains constant

20. Practice Problems The volume of a gas at 30 degrees celcius is 8.54 L. The pressure is increased from 760 mm Hg to 943 mm Hg. If the temperature increases 8 degrees celcius, what is the new volume? A 2.7 L container filled with carbon monoxide at 400 K has a pressure of 5.7 atm. If the container is compressed to a volume of 1.0 L and a pressure of 6.0 atm, how will the temperature change? What is the new temperature?

21. Classwork/Homework Please work in your books on the practice sections of pg 315, 319, 320, 322 If you do not finish this in class, please finish it for homework

22. Ideal Gas Law PV = nRT“piv nurt” n - number of moles R - gas constant ◦ Values of R:  0.0821atm  62.4mmHg  8.31kPa V in L T in K n in mol

23. Practice Problems Exactly 1 mole of carbon dioxide is in a 4.0 L container at 283 K, what is the pressure the gas exerts? 2.4 moles of gas is exerting 760 torr on a 30.0 L container, what is the temperature of the gas in Celsius? A gas is contained in 2.87 L container at 300 K. The pressure exerted is 220. kPa. If the gas is CO 2, what mass of the gas is in the container?

24. Ideal Gas Law Molar Mass ◦ MM = gRT/PV Gas Density ◦ D= m/vd = PMM/RT ◦ As temperature increases, volume increases ◦ As volume increases and mass remains the same, density decreases

25. Practice Problems 6.00 g of He is contained in a box at STP, what is the volume of the box? Calculate the density of a gas with a molar mass of 132 g/mol at STP. Neon gas is contained in a 55 L container at 297 K; if the neon exerts a pressure of 1000. torr, what is the mass of the gas?

26. HW Pg 357 ◦ 16-19 letter c only ◦ 20 ◦ 21

27. Graham’s Law of Diffusion v1=d2v1=m2 v2d1v2m1 v – rate of diffusion d – density m – molar mass

28. Practice Problems Calculate the relative rates of diffusion of O 2 and H 2 H subscript 1, O subscript 2 Answer: molecule 1 is 4 times molecule 2 ◦ H 2 is 4 times faster than O 2 /diffuses 4x faster

29. Practice Problems If equal amounts of helium and argon are placed in a porous container and allowed to escape, which gas will escape faster and how much faster? What is the molecular weight of a gas which diffuses 1/50 as fast as hydrogen? How much faster does hydrogen escape through a porous container than sulfur dioxide?

30. Collecting a gas over water P atm = P gas + P H 2 0 P H 2 0 depends on temperature

31. Practice Problems If we collected 310.0 mL of gas over water at a pressure of 738 mmHg and a temperature of 20.0°C, what is the partial pressure in atm of H 2 (g) in the test tube? 193 mL of O 2 was collected over water on a day when the atmospheric pressure was 762 mmHg. The temperature of the water was 23.0 o C. How many grams of oxygen were collected?