1. Dalton’s Law of Partial Pressures

2. In a mixture of non-reacting gases
Each gas particle behaves independently
Particles spread themselves out to occupy the space available
According to the KMT, pressure is caused by collisions with the walls of the container

3. Dalton’s Law of Partial Pressures
The total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases.
Ptot = P1 + P2 + P3 + …

6. Partial Pressures of Atmospheric Gases
Air consists of a mixture of gases:
N2 = 78.08% O2 = 20.95%
Ar = 0.93 % CO2 = 0.03%
If Standard atmospheric pressure is kPa, determine the partial pressure of each gas.

7. Gas Collection over Water
Gases can be collected by bubbling them through water.
The gas collected is a mixture of the desired gas and water.
To find the partial pressure of the desired gas, the vapour pressure of water must be subtracted.

8. Gas Collection over Water
Hydrogen gas from the reaction of Zinc with hydrochloric acid was collected by the displacement of water. Atmospheric conditions were kPa and 20˚C.
Determine the partial pressure of hydrogen gas.
Ptot = Patm = PH2 + PH2O
PH2 = Patm - PH2O
= kPa kPa
= 98.2 kPa

9. Homework
Read p
P. 461 #1-3
P. 463 #5
P. 465 #8-10; #1-7