1. Gas Laws and Gas Stoichiometry

2. Kinetic –Molecular Theory Particles of matter (solid, liquid, or gas) are always in motion. This motion has consequences. Solid (defined shape and definite volume) Liquid (undefined shape and definite volume) Gases (undefined shape and volu)me

3. Kinetic-Molecular Theory of Gases Gases are large numbers of tiny particles Particles always moving in straight lines in all directions. Therefore, they have “kinetic energy” These particles have elastic collisions between other particles and the container Elastic – no loss of KE after collision There is no attraction or repulsion between the particles Kinetic energy of the particles is proportional to the temperature of the matter

4. Ideal Gas vs. Real gas Ideal Gas: Completely follows kinetic molecular theory (K-M theory) of gases Hydrogen, maybe Helium, sometimes Real Gas: Does not behave by K-M theory

5. K-M theory and nature of gases Expansion Fluidity (liquids and gases) Low Density Compressibility Diffusion

6. Characteristics 1.Expansion 2.Fluidity

7. Characteristics 3. Low density

8. Characteristics 4.Compressibility

9. Characteristics Diffusion

10. 4 quantities that can be measured Volume – How much space it takes up Pressure – Amount of collisions particles have with container Temperature – Average kinetic energy of the gas particles Quantity or number of molecules – moles We use these quantities to “work” with gases

11. Pressure Pressure = Force / Area Units of Pressure 1 atm = 760 mm Hg = 760 torr = 1.01 x 10 5 pascals

12. Convert a pressure of 0.830 atm to mmHg

13. Temperature Scales Absolute zero = -273.15 o C = 0 K (not 0 o K) Therefore K = 273 + o C 0 o C = 273 K As temperature increases, the number of gas collisions increases.

14. Temp. conversions K = o C + 273 25.0 o C = ? K

15. STP “Slap The Pupils” -- No “Such Total Pigs” -- No Standard Temperature and Pressure The volume of a gas depends on temperature and pressure. In order to compare volumes of gases, need a standard. 0 degrees Celsius, 273 K 1 atm of pressure

16. Boyle’s Law Volume off a fixed mass of gas varies inversely with pressure at a constant temperature

17. Boyle’s Law P 1 V 1 = k and P 2 V 2 = k Therefore P 1 V 1 = P 2 V 2

18. A sample of oxygen gas occupies a vol. of 150 mL at a pressure of 720 mmHg. What would the volume be at 750 mmHg press.?

19. France, early 1800’s Hot air balloons were extremely popular Scientists were eager to improve the performance of their balloons. Two of the prominent French scientists were Jacques Charles and Joseph-Louis Gay-Lussac,

21. Charles’ Law The volume of a fixed mass of gas varies directly with the Kelvin temperature at constant pressure

23. Charles’ Law V 1 / T 1 = V 2 / T 2

24. A sample of Ne gas has a vol. of 752 mL at 25.0 deg. C. What is the vol. at 50.0 deg. C? T 1 = 25.0 deg. C = 298 K T 2 = 50.0 deg C = 323 K V 1 = 752 mL

25. Gay-Lussac’s Law The pressure of a fixed mass of gas varies directly with the Kelvin temp. at constant volume P 1 / T 1 = P 2 / T 2

27. A sample of N gas is at 3.00 atm of pressure at 25 deg C what would the pressure be at 52 deg C? P 1 = 3.00 atm T 1 = 25 deg C = 298 K T 2 = 52 deg C = 325 K P 2 = ? P 1 / T 1 = P 2 / T 2 or P 2 = P 1 T 2 / T 1

28. Combined Gas Law Relates Pressure, Volume, and Temperature Notice it is a combination of Boyles, Charles, and Gay-Lussac’s Laws P 1 V 1 / T 1 = P 2 V 2 / T 2

29. A helium filled balloon has a vol. of 50.0 L at 25 deg C and 820. mmHg of pressure. What would the vol. be at 650 mmHg pressure and 10. deg C? P 1 V 1 / T 1 = P 2 V 2 / T 2 V 1 = 50.0 L T 1 = 25 deg C = 298 K P 1 = 820. mmHg T 2 = 10. deg C = 283 K P 2 = 650 mmHg V 2 = ?

30. Molar Volume of a Gas One mole of a gas has the same volume at STP as any other gas 22.4 L / mole at STP

31. What volume would 0.0680 mol of oxygen gas occupy at STP? What about 0.0680 mol of nitrogen gas at STP? Practice Problem

32. Ideal Gas Law PV = nRT n = Number of Moles R = Ideal Gas Constant 0.0821 atm*L / mol*K V = Volume (must be in liters) P = Pressure (must be in atmospheres) T = Temperature (must be in Kelvin)

33. Practice Problem What is the P (in atm) exerted by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K? Pressure = 1.22 atm

34. Gas Stoichiometry  Uses volume-volume calculations (e.g. L  L)  Liters can be used just like mole to mole ratios in a factor label problem

35. Practice Problem How many L of oxygen are required for the complete combustion of 0.250 L of propane? C 3 H 8 (g) + 5O 2 (g)  3CO 2 (g) + 4H 2 O(g)  5 L O 2 needs 1 L C 3 H 8

36. Practice Problem How many grams of calcium carbonate must be decomposed to produce 2.00 L of CO 2 at STP? CaCO 3 (s)  CaO(s) + CO 2 (g) 2.00 L CO 2 x 1 mol CO 2 x 1 mol CaCO 3 X 100.086 g CaCO 3 22.4 L CO 2 1 mol CO 2 1 mol CaCO 3 = 8.94 g CaCO 3