Grahams Law
http://www.youtube.com/watch?v=FCVjyS4bQwg
Sample Problems
Problem #1: If equal amounts of helium and argon are placed in a porous
container and allowed to escape, which gas will escape faster and how much
faster?
Solution:
Set rate1 = He = x
Set rate2 = Ar = 1
The molecular weight of He = 4.00 The molecular weight of Ar = 39.95
Graham's Law is:
r1 over r2 = √MM2 over √MM1
Substituting, we have:
x / 1 = √(39.95 / 4.00)
x = 3.16 times as fast.
Problem #2: What is the molecular weight of a gas which diffuses 1/50 as fast as
hydrogen?
Solution:
Set rate1 = other gas = 1
Set rate2 = H2 = 50
The molecular weight of H2 = 2.02 The molecular weight of the other gas
= x.
By Graham's Law (see the answer to question #1), we have:
1 / 50 = √(2.02 / x)
x = 5050 g/mol
You Practice:
1. If He has an effusion rate of 0.00104moles/sec. What would the
effusion rate for CH3Cl be in moles/sec
2. If 0.0573 moles of C2H2 effuses in 776seconds, how many seconds
would it take for the same number of moles of Xe to effuse?
Dalton’s Law of Partial Pressure
http://www.youtube.com/watch?v=xDI9y4D2sFU
Dalton’s Law Worksheet
1)
A metal tank contains three gases: oxygen, helium, and nitrogen. If the
partial pressures of the three gases in the tank are 35 atm of O2, 5 atm of N2,
and 25 atm of He, what is the total pressure inside of the tank?
2)
Blast furnaces give off many unpleasant and unhealthy gases. If the total air
pressure is 0.99 atm, the partial pressure of carbon dioxide is 0.05 atm, and
the partial pressure of hydrogen sulfide is 0.02 atm, what is the partial
pressure of the remaining air?
3)
If the air from problem 2 contains 22% oxygen, what is the partial pressure
of oxygen near a blast furnace?
Dalton’s Law Worksheet Answers
1)
A metal tank contains three gases: oxygen, helium, and nitrogen. If the
partial pressures of the three gases in the tank are 35 atm of O2, 5 atm of N2,
and 25 atm of He, what is the total pressure inside of the tank?
65 atm
2)
Blast furnaces give off many unpleasant and unhealthy gases. If the total air
pressure is 0.99 atm, the partial pressure of carbon dioxide is 0.05 atm, and
the partial pressure of hydrogen sulfide is 0.02 atm, what is the partial
pressure of the remaining air?
0.92 atm
3)
If the air from problem 2 contains 22% oxygen, what is the partial pressure
of oxygen near a blast furnace?
0.92 x 0.22 = 0.20 atm