1

Ch 10.1

• Kinetic Theory: 5 assumptions1. small particles - far apart

2. Movement random, rapid & continuous

3. Collisions are elastic

4. No attractive/repulsive forces

5. Average kinetic energy depends on temp.

2

Ch 10.1• Properties specific to gases:

– Expand– Compress– Low density– Fluid– Diffuse: [↑]to [↓] until equal

• Rate depends on, speed, diameter, attractive force

• Calculated by v1 m2

• v2 m1

• Effuse: force through small opening.– Joule Thomas effect

3

Ch 10.2

– Note: the lower the temp of a gas the more “ideal” it is

– Pressure = caused by the collisions of gas particles against it’s container.

– Standard Pressure units• 101.3 kPa=• 760mmHg or Torr for Torricilli (barometer)• 1 ATM

– STP = standard temp and pressure

4

Ch 10.2

• Standard Temperature– 0 oC or 273 K

• Temp is a measure of kinetic energy

• Kinetic energy = mv2 / 2

• Absolute zero is where (theoretically) all particle motion ceases.-273 oC or 0 K

5

Ch 10.3

• In 1662 Robert Boyle: If amount and temp remain the same then,

• Boyle’s Law = P1V1 = P2V2

• Inverse proportion: As one goes up the other goes down.

6

Ch 10.3

• 1787 Jacques Charles showed that the volume of a gas varied directly with Kelvin temp

• Charles’ Law: V1 = V2

• T1 T2

• K= oC + 273

• *** always calculate in Kelvin for gases***

7

Ch 10.3

• 1802 Joseph Gay-Lussac recognized that for each 1oC increase the volume would increase by 1/273.

• Therefore at -273oC a gas would have no volume or disappear BUT ALL gases turn to liquid before this happens.

• He also noticed : P1 = P2

• T1 T2

8

Ch 10.3

• The Combined Gas Law:

P1V1 = P2V2

T1 T2

9

Ch 10.3

• John Dalton found that in the absence of a chem rxn the pressure of a gas mixture is the sum of the individual gas pressures.

• The partial pressure is the pressure of one gas in a mixture so it’s only part of the total pressure!

• P total = P gas + P other gases

• P gas = P total – P other gases

10

CH 10.3

• When a gas is collected through water displacement –The left over water vapor pressure exerts a pressure that must be accounted for.

• Use a water vapor chart (pg 899)

• Pgas = Patm – PH2O at what ever temp

•

11

CH 10.3

• A sample of Oxygen gas is collected in a 175ml container over water at 15oC and the barometer read 760 torr. What volume will the dry gas occupy at 770torr and 15oC.

• Adjusting for the water vapor 760 torr - 12.8 torr = 747.2 torr should be used instead of 760 torr.

12

IDEAL GAS Law

• Ideal Gas equation is derived at by combining all 4 variables concerned with the physical characteristics of gases (volume, temperature, pressure & # of particles)

13

IDEAL GAS Law

• Ideal Gas Equation: PV=nRT

• R is a constant used in calculations involving the ideal gas equation

• R= .0820 L•Atm

• mol•K

• R = (1atm)(22.4L)/ (1mol)(273K)

• n = number of moles

14

Molecular Mass and Density

• The calculation of the molecular mass (M) and Density (D) can be determined using the ideal gas equation.

• M = mRT D= MP

PV RT

This is important in determining the formulas and structures of unknown compounds.