Cliffs AP Chemistry, 3rd Edition

ideal gas law: PV = nRT

R = 0.0821 liter ⋅atm / mole ⋅K

= 8.31 liter ⋅kPa / mole ⋅K

= 8.31 J / mole ⋅K

= 8.31 V⋅C / mole ⋅K

= 8.31 × 10 –7g ⋅cm^2 / sec^2 ⋅mole ⋅K

(for calculating the average speed of molecules)

= 6.24 × 104 L ⋅mm Hg / mole ⋅K

= 1.99 cal / mole ⋅K

weight MW PV

gRT

molecular :

::

==

van der Waals (real gases): (P + a/V^2 )(V−b) = R ⋅T

or

(P + n^2 a/V^2 )(V −nb) = n ⋅R ⋅T

Here acorrects for force of attraction between gas molecules, and bcorrects for particle

volume.

• Graham’s law of effusion:

r

r

d

d

t

t

u

u

MW

MW

2

1

1

2

1

2

2

1

1

==^2 ==

where

r= rate of effusion

d= density

MW = molecular weight

t= time

u= average speed

• Kinetic Molecular Theory
  
  
  1. Gases are composed of tiny, invisible molecules that are widely separated from one
     another in empty space.
  
  
  2. The molecules are in constant, continuous, random, and straight-line motion.
  
  
  3. The molecules collide with one another, but the collisions are perfectly elastic (no net
     loss of energy).
  
  
  4. The pressure of a gas is the result of collisions between the gas molecules and the
     walls of the container.
  
  
  5. The average kinetic energy of all the molecules collectively is directly proportional to
     the absolute temperature of the gas. Equal numbers of molecules of any gas have the
     same average kinetic energy at the same temperature.
  
  
  
  

Part II: Specific Topics