Ch 10 lecture notes, part 2

5/13/2014
Chapter Outline












10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
10.10
10.11
10.12
The Properties of Gases
Effusion and the Kinetic Molecular Theory of Gases
Atmospheric Pressure
Relating P,T, and V: The Gas Laws
The Combined Gas Law
Ideal Gases and the Ideal Gas Law
Densities of Gases
Gases in Chemical Reactions
Mixtures of Gases
Solubilities of Gases and Henry’s Law
Gas Diffusion: Molecules Moving Rapidly
Real Gases
Torricelli’s Barometer
Pressure = force/unit area
Molecules collide with the inside surface of the container.
The force of the collision is measured as pressure.
Pressure at Sea Level
Pounds/in2 (psi)
14.7 psi
Atmospheres (atm)
Pascals (N/m 2)
Torr (mmHg)
1 atm
101.325 X 103 Pa
760 mmHg
Elevation and Atmospheric
Pressure
vacuum
Column of
mercury
760 mm Hg
Atmospheric
pressure
The pressure of the
atmosphere on the surface
of the mercury in the dish
is balanced by the
downward pressure
exerted by the mercury in
the column.
0.35 atm
0.62 atm
0.83 atm
Sea level
Chapter Outline












10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
10.10
10.11
10.12
The Properties of Gases
Effusion and the Kinetic Molecular Theory of Gases
Atmospheric Pressure
Relating P,T, and V: The Gas Laws
The Combined Gas Law
Ideal Gases and the Ideal Gas Law
Densities of Gases
Gases in Chemical Reactions
Mixtures of Gases
Solubilities of Gases and Henry’s Law
Gas Diffusion: Molecules Moving Rapidly
Real Gases
State Variables for a Gas
P = pressure
V = volume
T = temperature
n = number of
moles
1
5/13/2014
Boyle’s Law: P and V
(n and T held constant)
Boyle’s Law and Respiration
 Gases are compressible
• Pressure ↑ as Volume ↓
 Boyle’s Law:
• P  1/V (T and n fixed)
• or, P × V = constant
• or, P1V1 = P2V2
• Decreasing volume increases
number of collisions/area; P↑
(KMT Postulates #3 & 4)
Sample Exercise 10.3:
Applying Boyle’s Law
Explaining Boyle’s Law Using Kinetic
Molecular Theory
A popular scuba tank for sport diving has an internal volume of 12.0 L
and can be filled with air up to a pressure of 232 bar. Suppose a diver
consumes air at the rate of 21 L/min while diving on a coral reef where
the sum of atmospheric pressure (1.0 bar) and water pressure averages
2.2 bar. How long will it take the diver to use up a full tank of air? The
temperature of the air and water on the reef are the same: 28 oC.
Charles’s Law: V and T
(n and P held constant)
 Charles’s Law:
• V  T (P, n constant)
V V
or, 1 = 2
T1 T2
Jacques Alexandre Charles (1796-1823)
The French chemist Charles was most famous in his lifetime for his experiments in
ballooning. The first such flights were made by the Montgollier brothers in June 1783,
using a large spherical balloon made of linen and paper and filled with hot air. In
August 1783, however, a different group. supervised by Jacques Charles, tried a
different approach. Exploiting his recent discoveries in the study of gases, Charles
decided to inflate the balloon with hydrogen gas. Because hydrogen would escape
easily from a paper bag, Charles made a bag of silk coaled with a rubber solution.
Inflating the bag to its final diameter took several days and required nearly 500
pounds of acid and 1000 pounds of iron to generate the hydrogen gas. A huge crowd
watched the ascent on August 27, 1783. The balloon stayed aloft for almost 45
minutes and travelled about 15 miles. When it landed in a village, however, the
people were so terrified they tore if to shreds.
Volume of a gas extrapolates
to zero at absolute zero (0 K
= −273°C).
Kinetic energy ↑ as T ↑; force of
collisions increases and gas
expands to maintain constant
P (KMT Post. #3, 4 & 5).
2
5/13/2014
Sample Exercise 10.4:
Applying Charles’ Law
Explaining Charles’ Law Using Kinetic
Molecular Theory
Several students at a northern New England campus are hosting a party
celebrating the mid-January start of “spring” semester classes. They
decide to decorate the front door of their apartment building with party
balloons. The air in the inflated balloons is initially 70 oF. After an hour
outside, the temperature of the balloons is -12 oF. Assuming no air leaks
from the balloons and the pressure in them does not change significantly,
how much does their volume change? Express your answer as a
percentage of the initial volume.
Avogadro’s Law: V and n
(T and P held constant)
Explaining Avogadro’s Law Using
Kinetic Molecular Theory
 Volume is directly proportional to the number
of moles of gas, V  n (T, P constant)
V
 constant
n
or ,
V1 V2

n1 n2
Increasing n increases the
number of collisions, gas
expands to keep pressure
constant (KMT Post. #3 & 4).
Amonton’s Law: P and T
(n and V held constant)
 P  T (n, V constant)
P
= constant
T
P P
or, 1 = 2
T1 T2
Sample Exercise 10.5:
Applying Amonton’s Law
Labels on aerosol cans caution against their incineration because the
cans may explode when the pressure inside them exceeds 3.00 atm. At
what temperature in degrees Celcius might an aerosol can burst if its
internal pressure is 2.00 atm at 25 oC?
Increasing T will increase force
of collisions if volume is kept
constant; P will increase (KMT
Post. #3, 4 & 5).
3
5/13/2014
Explaining Amonton’s Law Using
Kinetic Molecular Theory
Chapter Outline












The Combined Gas Law
Combining Boyle’s and Charles’ Law (where n is held constant)
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
10.10
10.11
10.12
The Properties of Gases
Effusion and the Kinetic Molecular Theory of Gases
Atmospheric Pressure
Relating P,T, and V: The Gas Laws
The Combined Gas Law
Ideal Gases and the Ideal Gas Law
Densities of Gases
Gases in Chemical Reactions
Mixtures of Gases
Solubilities of Gases and Henry’s Law
Gas Diffusion: Molecules Moving Rapidly
Real Gases
Sample Exercise 10.6:
Applying the Combined Gas Law
The pressure inside a weather balloon as it is released is 798 mmHg. If
the volume and temperature of the balloon are 131 L and 20 oC, what is
the volume of the balloon when it reaches an altitude where its internal
pressure is 235 mmHg and T = -52 oC?
4

Download Report