Chapters 2  6:
examined components
Chapters 7:
examine bulk properties
Gases
Gas Laws
variable:
amount
(n)
unit:
mole (mol)
Ideal Gas Law Constant:
R
R = 0.0821
atm•L
K•mol
Variables of state and their units:
variable:
pressure (P)
unit:
atmosphere (atm)
variable:
volume (V)
unit:
liter (L)
conversion factors:
variable:
temperature (T)
unit:
Kelvin (K)
conversion factor:
K =
o
C+273
1 atm
760 mm Hg
1 atm
760 torr
Section 7.1
766 mm Hg
∆
H = + 18 mm
P
gas
= P
atm
+
∆
H = 766
18
Section 7.1
Trapped gas is
greater/less
than 766 mm Hg?
It’s pushing harder
= 784 mm Hg
+
766 mm Hg
∆
H = 25 mm
P
gas
= P
atm
+
∆
H = 766
25
Section 7.1
Trapped gas is
greater/less
than 766 mm Hg?
It’s not
Pushing as hard
= 741 mm Hg

766 mm Hg
∆
H = 12 mm
What is the pressure of the gas in the bulb?
How do I get that pressure from mm Hg to atmospheres?
Section 7.1
Ideal Gas Law
PV = nRT
PV = nRT
Keep constant
P
i
V
i
=
P
f
(8 atm)
(4 atm)(4 L) =
16 atm•L
V
f
(2 L)
16 atm•L
Inversely
proportional
Boyle’s Law
Section 7.1
Demo: the belljar balloon
And the Cartesian Diver
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proportional
Charles’ Law
V
i
T
i
4 L
1 L/K
4 K
V
f
8 L
1 L/K
=
8 K
=
T
f
Ideal Gas Law
PT
PT
V = nR
P
T
PV = nRT
Keep constant
PV = nRT
Section 7.1
Demo: balloon and N
2
Absolute Temperature
The temperature at which any number of moles of
gas has a volume of ZERO is O Kelvin
(Otherwise known as –273.15 C)
Section 7.1
Directly
proportional
V
x
n
x
11.2 L
22.4 L/mol
0.5 mol
V
z
22.4 L
22.4 L/mol
=
1 mol
=
n
z
Avagadro’s Law
Ideal Gas Law
Pn
Pn
V = RT
P
n
PV = nRT
Keep constant
PV = nRT
Section 7.1
Demo: blowing a
balloon up
PV = nRT
Keep constant
VT
TV
P = nR
V
T
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 Fall '08
 BIGHAM
 Chemistry, pH, Thermal Energy, mm Hg

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