1. Gases Chapter 10/11 Modern Chemistry
Sections 10.1,
The Kinetic Molecular Theory of Matter
Gases and Pressure
The Gas Laws
Gas Volumes and the Ideal Gas Law
Chapter 8 Section 1 Describing Chemical Reactions p

2. Gas Volumes and the Ideal Gas Law
Section 11.3
Gas Volumes and the Ideal Gas Law
Chapter 11 Section 3 Ideal Gas Law p

3. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Comparing Gas Volumes
Chapter 11 Section 3 Ideal Gas Law p
p. 380

4. Law of Combining Volumes
Gay-Lussac’s Law of Combining Volumes of Gas
“At constant temperature and pressure, the volumes of gaseous reactants and products can be expressed as ratios of small whole numbers.”
H2 (g) O2 (g)  H2O (g)
2L L L
This could be any volume units.
Chapter 11 Section 3 Ideal Gas Law p

5. Combining Volumes of Gases
Chapter 11 Section 3 Ideal Gas Law p
p. xx

6. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Combining Volumes
Insert Holt Visualizing Matter Disc 2
Chapter 11 Section 3 Ideal Gas Law p
p. xx

7. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Avogadro’s Law
“Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.”
2H2 (g) O2 (g)  2H2O (g)
2 molecules 1 molecule 2 molecules
2 moles mole moles
2 volumes 1 volume volumes
Chapter 11 Section 3 Ideal Gas Law p

8. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Avogadro’s Law
Same volume – Same number of particles
The type of gas doesn’t affect this relationship.
At STP, one mole of any gas occupies 22.4 L.
Chapter 11 Section 3 Ideal Gas Law p

9. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Molar Volume
Chapter 11 Section 3 Ideal Gas Law p
p. 379

10. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Molar Volume of a Gas
The volume occupied by one mole of gas at STP is know as the standard molar volume of a gas.
L / 1 mole
22.4 L / mole
Chapter 11 Section 3 Ideal Gas Law p

11. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Molar Volume Problems
a. What volume does mol of gas occupy at STP?
b. What quantity of gas, in moles, is contained in 2.21 L at STP?
p. 381
mol
Chapter 11 Section 3 Ideal Gas Law p

12. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Practice Problems p. 381
At STP, what is the volume of 7.08 mol of nitrogen gas?
A sample of hydrogen gas occupies 14.1 L at STP. How many moles of the gas are present?
p. 381
159 L N2
mol H2
Chapter 11 Section 3 Ideal Gas Law p

13. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Density of Gases at STP M
44.01 g CO2 D= =
= g/L CO2 V
22.4 L CO2
For a one mole sample of gas
M = molar mass = ________ g
V = molar volume = 22.4 L
Chapter 11 Section 3 Ideal Gas Law p

14. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Gas Density
Insert Holt Visualizing Matter Disc 2
Chapter 11 Section 3 Ideal Gas Law p

15. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Gas Density Problem
What is the density of C3H8 gas at STP?
g/L
Chapter 11 Section 3 Ideal Gas Law p

16. Practice Problems What is the density of nitrogen gas at STP?
What is the density of CH4 gas at STP?
g/L g/L
Great News! We’ve bred a cow that doesn’t release any methane.
Chapter 11 Section 3 Ideal Gas Law p

17. Chapter 11 Section 3 Ideal Gas Law p. 378-385
“The mathematical relationship among pressure, volume, temperature and the number of moles of a gas”
Nothing is held constant; one set of conditions.
P V = n R T
atm
kPa
mmHg
Kelvin
moles
constant
liters
Chapter 11 Section 3 Ideal Gas Law p

18. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Boyle’s Law
Charles Law
Gay-Lussac’s Law P V R = T n
Chapter 11 Section 3 Ideal Gas Law p

19. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Ideal Gas Constant p.384
Chapter 11 Section 3 Ideal Gas Law p

20. Deriving the Ideal Gas Law
Chapter 11 Section 3 Ideal Gas Law p

21. Ideal Gas Law Animation
Chapter 11 Section 3 Ideal Gas Law p
p. 383

22. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Ideal Gas Law Problems
What is the pressure in atmospheres exerted by a mol sample of nitrogen gas in a 10.0 L container at 298 K?
p. 385
atm
Chapter 11 Section 3 Ideal Gas Law p

23. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Ideal Gas Law Problems
An unknown gas has a density of g/mL at a pressure of atm and a temperature of 10.°C. What is the molar mass of the gas?
p. 898 #289
663 g/mol
Chapter 11 Section 3 Ideal Gas Law p

24. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Practice Problems p. 385
What pressure, in atmospheres, is exerted by mol of hydrogen gas in a 4.08 L container at 35°C?
A gas sample occupies 8.77 L at 20°C.What is the pressure, in atmospheres, given that there are 1.45 mol of gas in the sample?
p. 385
atm atm
Chapter 11 Section 3 Ideal Gas Law p

25. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Gas Stoichiometry
Three new “tools”
Law of Combining Gas Volumes
Use the coefficients (works with gases only)
Molar volume
22.4 L / 1 mole (works at STP only!)
Ideal Gas Law
PV = nRT
A way to convert from moles to liters if the conditions are not STP
Chapter 11 Section 3 Ideal Gas Law p

26. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Gas Stoichiometry
Propane, C3H8, is a gas that is sometimes used as a fuel for cooking and heating. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
What will be the volume, in liters, of oxygen required for the complete combustion of L of propane?
What will be the volume of carbon dioxide produced in the reaction? Assume that all volume measurements are made at the same temperature and pressure.
p. 382
1. (a) 1.75 L O2 (b) 1.05 L CO2
Chapter 11 Section 3 Ideal Gas Law p

27. Gas Stoichiometry Problem
Assuming all volume measurements are made at the same temperature and pressure, what volume of hydrogen gas is needed to react completely with 4.55 L of oxygen gas to produce water vapor?
p. 382
L H2
Chapter 11 Section 3 Ideal Gas Law p

28. Gas Stoichiometry Problem
Zinc and hydrochloric acid react to produce hydrogen gas. If 5.00 grams of zinc is reacted with excess acid at STP, how many liters of gas will be produced?
1.71 liters
Chapter 11 Section 3 Ideal Gas Law p

29. Gas Stoichiometry Problem
Baking soda and vinegar react to produce carbon dioxide gas. If 17.0 grams of baking soda are reacted with excess vinegar, how many liters of carbon dioxide will be produced at STP?
NaHCO3 (aq)+ HC2H3O2 (aq)  CO2 (g)+ H2O (l)+ NaC2H3O2 (aq)
4.53 L
Chapter 11 Section 3 Ideal Gas Law p

30. Gas Stoichiometry Problem
In the decomposition of H2O2 solution, water and oxygen form. If the oxygen gas is collected over water at 25.0 C and a total pressure of 92.1 kPa, what volume of gas , in liters, can be expected to form if 18.0 grams of H2O2 are decomposed?
7.38 L
Chapter 11 Section 3 Ideal Gas Law p

31. Gas Stoichiometry Problem
How many liters of ozone, O3 can be destroyed at 200. K and 7.00 kPa if 100. grams of chlorine gas reacts according to the following equation.
Cl2 + 2O3  2ClO + 2O2
670 L
Chapter 11 Section 3 Ideal Gas Law p

32. Gas Stoichiometry Problem
When 2.50 L of C3H8 at STP burns, what total volume of gaseous products is formed? The volume of the products is measured at 175°C and 1.14 atm.
C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (g)
p. 899 # 311 d.
answer
Chapter 11 Section 3 Ideal Gas Law p

33. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Air Bag Reactions
Insert McMurry Fay Chemistry Disc 1
Chapter 11 Section 3 Ideal Gas Law p

34. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Ch 11 Sec 3 Homework
Combined and Ideal Gas Law Problems Page 897 # 268, 272, 273; Page 898 # 287, 292, 294; Page 899 #300
Chapter 11 Section 3 Ideal Gas Law p

35. Chapter 11 Section 3 Ideal Gas Law p. 378-385
Ch 11 Sec 3 Homework
Gas Stoichiometry Problems Page 899 #310a, 312, 314 a-c, 315 
Chapter 11 Section 3 Ideal Gas Law p