1. Topic: Pressure (and Partial Pressure) Do Now: Convert the following units of pressure 249 torr to atm 10432 Pa to kPa 2534 kPa to mmHg

2. What causes the pressure of a gas in a closed container? Impacts of gas molecules with walls of container Pressure depends on:Pressure depends on: – # impacts per unit time – Force each impact Microscopic View

3. Light molecules move faster and hit walls more often Heavy molecules hit walls with greater force These 2 effects essentially balance out **Gas pressure doesn‘t depend on the identity(light like He (g) or heavy like CO 2(g) ) of the gas**

4. Molecular Speeds at 298 K H 2 1.93 X 10 5 cm/secH 2 1.93 X 10 5 cm/sec He1.36 X 10 5 cm/secHe1.36 X 10 5 cm/sec O 2 4.82 X 10 4 cm/sec *O 2 4.82 X 10 4 cm/sec * Ar4.31 X 10 4 cm/secAr4.31 X 10 4 cm/sec Xe2.38 X 10 4 cm/secXe2.38 X 10 4 cm/sec 48200 cm 1 in 1 ft 1 mile 3600 sec = sec 2.54 cm 12 in 5280 ft 1 hour 1080 miles per hour

5. Dalton’s Law of Partial Pressure The sum of individual pressures of all the gasses that make up a mixture is equal to the total pressure of the mixture P T = P 1 + P 2 + P 3 +…

6. 1 atm = Pressure of N 2 + Pressure of O 2 + pressure of Ar + pressure of H 2 ) (g) + …….. In order to figure Partial Pressure of N 2 = 1 atm (.7655) =.7655atm