Sections 10.1, 11.1-11.3
The Kinetic Molecular Theory of Matter
Gases and Pressure
The Gas Laws
1
Chemical Reactions p. 261-275

Chapter 11 Section 3 Ideal Gas
Law p. 378-385
2

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

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.”
H
2 (g)
+ O
2 (g)
 H
2
O
(g)
2L 1L 2L
This could be any volume units.
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
4

p. xx
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
5

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

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

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. 378-385
8

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

The volume occupied by one mole of gas at STP is know as the standard molar volume of a gas.
22.41410 L / 1 mole
22.4 L / mole
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
10

Molar Volume Problems a. What volume does 0.0685 mol of gas occupy at STP?
b. What quantity of gas, in moles, is contained in 2.21 L at STP?
1.
0.0987 mol
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
11

Practice Problems p. 381
1. At STP, what is the volume of 7.08 mol of nitrogen gas?
2. A sample of hydrogen gas occupies 14.1 L at STP. How many moles of the gas are present?
1. 159 L N
2
2.2.
0.629 mol H
2
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
12

D=
M
V
=
44.01 g CO
2
22.4 L CO
2
= 1.799 g/L CO
2
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. 378-385
13

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

Gas Density Problem
1. What is the density of C
3
H
8 gas at STP?
1.
1.9684 g/L
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
15

Practice Problems
1. What is the density of nitrogen gas at
STP? 1.
1.251 g/L
2.
0.7156 g/L
2. What is the density of CH
4 gas at STP?
Great News! We’ve bred a cow that doesn’t
Chapter 11 Section 3 Ideal Gas 16 release any methane.

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

Boyle’s Law
Charles Law
Gay-Lussac’s Law
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
18

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

Ideal Gas Law Problems
1. What is the pressure in atmospheres exerted by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K?
1.
1.22 atm
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
22

Ideal Gas Law Problems
An unknown gas has a density of 0.0262 g/mL at a pressure of 0.918 atm and a temperature of 10.
°C. What is the molar mass of the gas?
663 g/mol
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
23

Practice Problems p. 385
1. What pressure, in atmospheres, is exerted by 0.325 mol of hydrogen gas in a 4.08 L container at 35 °C?
2. 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?
1.
2.01 atm
2.
3.98 atm
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
24

• 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
• P V = n RT
•A way to convert from moles to liters if the conditions are not STP
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
25

1. Propane, C
3
H
8
, is a gas that is sometimes used as a fuel for cooking and heating.
C
3
H
8( g )
+ 5O
2( g )
→ 3CO
2( g )
+ 4H
2
O
( g )
(a)What will be the volume, in liters, of oxygen required for the complete combustion of
0.350 L of propane?
(b)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
.
1. (a)
1.75 L O
2
(b) 1.05 L CO
2
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
26

Gas Stoichiometry Problem
1. 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?
1.
9.10 L H
2
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
27

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. 378-385
28

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?
NaHCO
3 (aq)
+ HC
2
H
3
O
2 (aq)

CO
2 (g)
+ H
2
O
(l)
+
NaC
2
H
3
O
2 (aq)
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
4.53 L
29

Gas Stoichiometry Problem
In the decomposition of H
2
O
2 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 H
2
O
2 are decomposed?
7.38 L
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
30

Gas Stoichiometry Problem
How many liters of ozone, O
3 can be destroyed at 200. K and 7.00 kPa if
100. grams of chlorine gas reacts according to the following equation.
Cl
2
+ 2O
3
 2ClO + 2O
2
670 L
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
31

Gas Stoichiometry Problem
When 2.50 L of C
3
H
8 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.
C
3
H
8 ( g )
+ 5O
2 ( g )
→ 3CO
2 ( g )
+ 4H
2
O
( g ) answer
Chapter 11 Section 3 Ideal Gas
Law p. 378-385
32

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

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. 378-385
34

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