Kinetic-Molecular Theory of Gases Notes#5

increases All particles are in constant motion. As temperature increases kinetic energy ? increases increases As gas particles move apart the volume ?

Point Masses Gas particles are treated as a point with no volume and no mutual attraction -this is because they’re so small compared to the distances between them.

STP Ideal Gases A theoretical gas with no volume and no attraction. A series of theories will be studied about ideal gases -standard pressure of 101.32 kPa -standard temperature of 0°C or 273K -standard conditions are abbreviated STP

Therefore: Kinetic theory explains properties of gases based on a molecular view. The assumptions are: The molecules are in continuous, random motion. A molecule has negligible volume. The forces between molecules are negligible. The average kinetic energy depends on the temperature.

Four Gas Law Variables Are: V = volume P = pressure T = temperature n = number of particles (Case is important)

Units of pressure SI unit is Pascal (Pa) 1Pa = 1 N/m2 derived from force 1atm = 760mm Hg = 760 torr = 101.3 kPa =14.7 psi 1torr = 1 mm Hg

. . . Boyle’s Law Relates volume and pressure -gas exerts pressure on its container’s walls -pressure depends on *number of molecules *average kinetic energy of the molecules . . Pressure = P .

. . . . . . . . Boyle’s Law Relates volume and pressure -gas exerts pressure on its container’s walls -pressure depends on *number of molecules *average kinetic energy of the molecules Plunger applies pressure (now 2P). -As pressure doubles, volume becomes ½. -(note the same number of particles now occupying ½ the space) . . . . . . . .

Boyle’s Law Boyle’s Law PV=k *P=pressure *V= volume *k=constant Experiments happen at room temperature(about 25ºC.) We need to convert the results to STP.

Boyle’s Law Since and then (substituting for k)

Boyle’s Law Since and then (substituting for k) or

Boyle’s Law Since and then (substituting for k) or Units pressure - kPa volume - cm3

Problem: a gas is collected in a 242 cm3 container at 87. 6 kPa Problem: a gas is collected in a 242 cm3 container at 87.6 kPa. What is its volume at STP? V1= P1= V2= P2= 242 cm3 87.6 kPa ? 101.325 kPa Think: pressure goes from 87.6 kPa to 101.325 kPa so Volume should be________ than 242 cm3 Math:

so Note: 209 < 242cm3 Now do CMC 358: 1, 2, 3(a,c,e) and 4(a,c,e).