Three More Laws

A. Ideal Gas Law
• The 4 th variable that considers the amount of gas in the system is
• Equal volumes of gases contain equal numbers of moles (varies directly w/V).
• Add moles to the combination gas law
P
1
V
1
P
2
V
2
=
T
1 n T
2 n

A. Ideal Gas Law
•You can calculate the # of n of gas at standard values for P, V, and T
PV
= R
Tn
(1 atm)(22.4L)
(273K)(1 mol)
UNIVERSAL GAS CONSTANT
R= 0.0821 atm∙L/mol∙K
R=8.315 kPa  L/mol  K
= R
You don’t need to memorize this value!

A. Ideal Gas Law
UNIVERSAL GAS CONSTANT
R= 0.0821 atm∙L/mol∙K
R=8.315 kPa  L/mol  K
You don’t need to memorize these values!

A. Example Problems
1. At what temperature will 5.00g of Cl
2 exert a pressure of 900 mm Hg at a volume of 750 mL?
2. Find the number of grams of CO
2 that exert a pressure of 785 mm Hg at a volume of 32.5 L and a temperature of 32 degrees Celsius.
3. What volume will 454 g of H
2 and 25 ° C.
occupy at 1.05 atm

• Diffusion
– The tendency of molecules to move toward areas of lower concentration .
• Ex: air leaving tire when valve is opened
• Effusion
– Passing of gas molecules through a tiny opening in a container

B. Graham’s Law
Diffusion
Tiny opening
Effusion
Which one is Diffusion and which one is Effusion?

C. Dalton’s Partial Pressure Law
• The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases.
P total
= P
1
+ P
2
+ P
3
+ ...

C. Dalton’s Law
• Exmple problem:
1. Air contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen (P
O2
) at 101.3 kPa of total pressure if the partial pressures of nitrogen, carbon dioxide, and other gases are 79.10 kPa,
0.040 kPa, and 0.94 kPa.
P
O2
= P total
– ( P
N2
+ P
CO2
+ P others
)
=
101.3 kPa – (79.10 kPa + 0.040 kPa + 0.94 kPa)
= 21.22 kPa