Consider the Haber Process: 3H2 (g) + N2 (g)<---> 2NH3 (g) + 92 Kj
What would be the effects of the following stresses on the concentration of NH3
once equilibrium is reestablished. Give a brief explanation for each.
a. increase [H2]
b. decrease [N2]
c. increase temperature
d. increase volume
e. increase pressure

A. An increase in the concentration of hydrogen leads to an increase
in the concentration of ammonia.

B.  A decrease in the concentration of nitrogen leads to a decrease in
the concentration of ammonia.

pNH3 = [pN2(pH2)^3Keq]^1/2.  The partial pressures of the various
components are related to their concentration [pj = nj/V x RT, where
nj/V is the concentration].  Therefore, one can see how an increase or
decrease in one affects the other.

The following three questions utilize Le Chatelier's principle, which
"...states that when a stress is applied to a system in equilibrium
the equilibrium conditions shift in such a way as to relieve the
stress."  (Page 633)

C.  An increase in temperature results in a decrease in the
concentration of ammonia.  To restore equilibrium, the reaction wants
to absorb the increase in heat.  The dissociation of ammonia is
endothermic, so the concentration of ammonia will be reduced.

D.  An increase in volume results in a decrease in the concentration
of ammonia.  To restore equilibrium, the reaction wants to increase
the number of moles of gas.  The dissociation of ammonia increases the
total number of moles of gas, so the concentration of ammonia will be
reduced.

E.  An increase in pressure results in an increase in the
concentration of ammonia.  To restore equilibrium, the reaction wants
to decrease the number of moles of gas.  The formation of ammonia
decreases the total number of moles of gas, so the concentration of
ammonia will be increased.

Source:

Chemical Principles, fourth edition, Dickerson, Gray, Darensbourg, and
Darensbourg, The Benjamin/Cummings Publishing Company, Inc., 1984

Sincerely,

Wonko