1. The Gas Laws
Chapter 14
Chemistry

2. Remember gases behave differently

3. Gases are affected by
Temperature
Pressure
Volume

4. Boyle’s Law Robert Boyle Relationship between pressure and volume
P1V1 = P2V2
Inverse relationship – As volume decreases, pressure increases

6. Example Problem
A sample of helium gas in a balloon is compressed from 4.0 L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0 L volume is 210 kPa, what will the pressure be at 2.5 L?
P1V1 = P2V2

7. Boyle’s Law Activity
Marshmallow in Syringe

8. Dalton’s Law of Partial Pressures
Total pressure of a mixture of gases is the sum of the pressures of the individual gases.

9. Charles’s Law Jacques Charles
Relationship between temperature and pressure
Direct Relationship
V1 = V2
T1 T2

11. Sample Problem
A gas sample at 40.0oC occupies a volume of 2.32 L. If the temperature is raised to 75oC, what will the volume be, assuming the pressure remains constant?

12. Charles’s Law Activity
Cold Balloon
Bottle Crush
Popcorn

13. Gay-Lussac’s Law Relationship between temperature and pressure
Volume must be held constant
Direct relationship
P1 = P2
T T2

14. Sample Problem
The pressure of a gas in a tank is 3.2 atm at 22.o oC. If the temperature rises to 60 oC, what will be the gas pressure in the tank?

15. Combined Gas Law
P1V1 = P2V2
T T2

16. Sample Problem
A gas at 110 kPa and 30.o oC fills a flexible container with an initial volume of 2.oL . If the temperature is raised to 80oC and the pressure increased to 440 kPa, what is the new volume?

17. Avagadro’s Principle
Equal volumes of gases at the same temperature and pressure contain equal numbers of particles
Molar volume = the volume one mole of gas occupies at 0oC and 1.0 atm pressure
One mole of any gas will occupy 22.4L

18. Practice Problem
Calculate the volume that 2.0 Kg of methane gas (CH4) will occupy at STP

19. Ideal Gas Law
Ideal gases have almost no volume and the particles are far enough apart to not exert any type of repulsive or attractive force on another particle.
Do not exist in real world, but most gases behave like ideal gases at STP
PV=nRT

20. Practice
Calculate the number of moles of gas contained in a 3.0L vessel at 3.00 x 102 K with a pressure of 1.5 atm
PV = nRT
P = 1.5 atm
V = 3.0L
R = .0821
T = 3oo K
N = ?

21. Gas Stoichiometry
Remember, coefficients represent the number of moles of a reactant or product
2 C4H O2  8 CO H2O

22. Calculations involving only volume
CH4 + 2 O2  CO2 + 2H2O
It takes 2 liters of oxygen to react with 1 L of methane to produce 1 liter of carbon dioxide and 2 liters of water

23. Volume to volume problem
What volume of oxygen gas is needed for the complete combustion of 4.0 L of propane gas (C3H8)? Assume constant pressure and temperature.
C3H8 + 5O2  3CO2 + 4H2O
Start with what you know: 4.0L C3H8
What is the ratio of Oxygen to propane? 5 oxygen
1 propane
3. Multiply the amount of propane by the ratio to get oxygen 5 x 4 = 20 L

24. Volume to Mass Problem
Ammonia is synthesized from hydrogen and nitrogen gases. N2 + 3H2  2 NH3
If 5.00 L of nitrogen reacts completely by this reaction at a constant pressure and temperature of 3.00atm and 298K, how many grams of ammonia are produced?

25. 1. Analyze problem (V, P, T, ) 2. Solve for unknown
Determine volume ratio
Use ratio to determine liters of ammonia produced
Rearrange and use ideal gas law to solve for n (use liters of ammonia produced as V)
3. Convert moles of ammonia to grams of ammonia