1.
Turn in Work Book 14.1 and 14.2
Get out your notes packet

2. Gases
Gas Animations

3. Kinetic Molecular Theory (Behavior of Gasses)
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.

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

5. **Most real gases act like ideal gases except under high pressure and low temperature.
Under these conditions the assumptions of the kinetic theory are too far from reality. This is when the gas laws (based on an ideal gas) will not accurately model real gas behavior.
Conditions where a gas has particles that are very close together.

6. Characteristics of Gases
Gases expand to fill any container.
Take the shape and volume of their container.
Gases are fluids (like liquids).
Little to no attraction between the particles
Gases have very low densities.
= lots of empty space between the particles

7. Characteristics of Gases
Gases can be compressed.
lots of empty space between the particles
Indefinite density
Gases undergo diffusion & effusion.
random motion
scatter in all directions

8. Temperature= how fast the molecules are moving
Always use absolute temperature (Kelvin) when working with gases. ºF ºC K
-459 32
212
-273
100
273
373
K = ºC + 273

9. Pressure
Which shoes create the most pressure?

11. Pressure Barometer measures atmospheric pressure Aneroid Barometer
Mercury Barometer
Aneroid Barometer

12. Pressure Manometer measures contained gas pressure U-tube Manometer
Bourdon-tube gauge
C. Johannesson

13. Pressure- how much a gas is pushing on a container.
Atmospheric pressure- atmospheric gases push on everything on Earth
UNITS AT SEA LEVEL
1 atm =101.3 kPa (kilopascal)= 760 mmHg =760 torr
=14.7 psi

14. Standard Temperature & Pressure
STP
STP
Standard Temperature & Pressure
0°C K
1 atm kPa
-OR-

15. n = moles = how much gas there is R = ideal gas constant
V = volume = how much space a gas occupies
Units
L, mL, cm3
1000 mL = 1 L, 1 mL = 1 cm3
n = moles = how much gas there is
R = ideal gas constant
= (L*atm)
(mol*K)
= 8.31 (L*kPa)

16. BASIC GAS LAWS P V T

17. Charles’ Law V1 = V2 T1 T2 T is always in K V T
T  V (temperature is directly proportional to volume)
T ↑ V↑ & T↓ V↓
V1 = V2
T T2 T is always in K
P and n = constant
Ex) A 25 L balloon is released into the air on a warm afternoon (42º C). The next morning the balloon is recovered on the ground. It is a very cold morning and the balloon has shrunk to 22 L. What is the temperature? V T

18. Charles’ Law Video
Link to video
A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.

19. Boyle’s Law
P↓ V ↑ & P↑ V ↓
P  1/V (pressure is inversely proportional to volume)
P1V1 = P2V2
T and n = constant
Ex: Pressure: kPa  0.92 atm
Volume: ? mL  8.0 L P V

20. A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa.
Not in Notes
A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa.

21. AVOGADRO’S LAW Vn Vn V n (direct) V1 = V2 n1 n2
T & P Constant
EX: A 3 liter sample of gas contains 3 moles. How much gas will there be, in order for the sample to be 2.3 liters? P & T do not change

22. EX: A 3 liter sample of gas contains 3 moles
EX: A 3 liter sample of gas contains 3 moles. How much gas will there be, in order for the sample to be 2.3 liters? P & T do not change

23. Gay-Lussac’s Law P1 = P2 T1 T2 Direct relationship PT PT  P
V & n constant
Direct relationship
PT PT 

24. Example: A can of Dust Off is sitting next to my computer at 25°C and 3.5 atm. I flip the can over and spray some air out. The room has a pressure of 1.0 atm. What is the temperature of the air as it escapes the container?
2.06 min

25. COMBINED IDEAL GAS LAW P1V1 = P2V2 n1T1 n2T2
If P, V, n, or T are constant then they cancel out of the equation.
n usually constant (unless you add or remove gas), so
T T2

26. Nitrogen gas is in a 7. 51 cubic centimeter container at 5C and 0
Nitrogen gas is in a 7.51 cubic centimeter container at 5C and 0.59 atm. What is the new volume of the gas at standard temperature and pressure?
A sample of chlorine gas has a pressure of 7.25 kPa at 20.0C and a volume of 16.0 mL. What will the pressure be at 60.0C if its volume does not change?

27. Warm up : GASSES!!!!!
Grab a quiz from the front – no notes, no cheating, turn it in up front when finished
Today we will be completing the Gas Notes
PiVNRT!!!!!!!!!
Test Make-up? – its almost the end of the 6 weeks!!!

28. A cylinder of gas has a pressure of 4. 40 atm at 25°C
*A cylinder of gas has a pressure of 4.40 atm at 25°C. At what temperature (°C) will it reach a pressure of 6.50 atm?

29. A 34 L sample of gas at 0. 0°C contracts to 17 L as it cools
*A 34 L sample of gas at 0.0°C contracts to 17 L as it cools. What is the new temperature?

30. A 6. 0 L sample of gas at 19 atm is compressed to 37. 3 atm
*A 6.0 L sample of gas at 19 atm is compressed to 37.3 atm. What is the new volume?

31. A 5. 6 L balloon contains 1. 2 moles of He
*A 5.6 L balloon contains 1.2 moles of He. How large will the balloon be with 3.4 moles of He?

32. Ideal Gas Law (“Pivnert”)
PV=nRT
R = The Ideal Gas Constant (memorize)
R = (L*atm)
(mol*K)
R = (L*kPa)
* Choose which R to used based on the units of your pressure. If you have mmHg change it to atm.
* V has to be in Liters, n in Moles, T in Kelvin, P can be in atm or kPa
P V = n R T
(atm) (L) = (moles) (L*atm/mol*K) (K)
(kPa) (L) = (moles) (L*kPa/mol*K) (K)

33. Numerical Values of the Gas Constant

34. A balloon contains 2. 00 mol of nitrogen at a pressure of 0
A balloon contains 2.00 mol of nitrogen at a pressure of atm and a temperature of 37C. What is the volume of the balloon?
Calculate the pressure (atm) of 2.79 g of F2 that occupies 5.00 L at 44.2C.

35. Dalton’s Law of Partial Pressure
The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases.
Ptotal = Pgas 1 + Pgas 2 + P­gas 3 + …
Example: Find the total pressure for a mixture that contains three gases. The partial pressure of nitrogen is kPa, helium is KPa, and oxygen is kPa.

36. Gases are collected over water
When a H2 gas is collected by water displacement, the gas in the collection bottle is actually a mixture of H2 and water vapor.
EX: Hydrogen gas is collected over water at 22.5°C. Find the pressure of the dry gas if the atmospheric pressure is 94.4 kPa. PH2O = 2.72 kPa

37. Many times you will be given the total pressure and the percent composition of the gas mixture. To find the pressure of the individual gases: For each gas, multiply the total pressure by the percent for that gas.
Example: A mixture of gases is 15.00% nitrogen, 45.00% oxygen, and 40.00% neon at 105.0kPa (OR SET IT UP AS A PROPORTION)

38. When given mole or volume amounts of each gas in the mixture: Set it up as a proportion.
Moles of part = Pressure of part
Total moles Total pressure
Volume of part = Pressure of part
Total volume Total pressure
   
Example: A tank contains a mixture of 5.0 mol N2, 2.5 mol O2, and 3.0 mol of CO2 at 38C and a total pressure of 5.5 atm. Calculate the partial pressure of each gas (in torr).

39. Example: A tank contains a mixture of 5. 0 mol N2, 2. 5 mol O2, and 3
Example: A tank contains a mixture of 5.0 mol N2, 2.5 mol O2, and 3.0 mol of CO2 at 38C and a total pressure of 5.5 atm. Calculate the partial pressure of each gas (in torr).

40. Effusion VS Diffusion
Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughout. = Spreading of gas molecules throughout a container until evenly distributed.
Effusion = gas escapes through a tiny hole in its container
Graham’s Law Rate of diffusion of a gas is inversely related to the square root of its molar mass.
= Gases of lower molar mass diffuse and effuse faster than gases of hi
gher molar mass.