before we began, and there will, of course, be more C and D particles.
To give you an idea of what we mean by “driving or shifting equilibrium to the
right,” consider this example.
Suppose for the reaction, 2A(g) + B(g) C(g), equilibrium concentrations
at a particular temperature are [A] = 2 M, [B] = 6 M, and [C] = 8 M.
When we plug these into the equilibrium expression Keq =
we get Keq = = .
Now, according to Le Chatelier’s principle, if we add more A into the system at
equilibrium, equilibrium will shift to the right. So once equilibrium is
reestablished, the concentration of C will be greater than 8 M, and the
concentration of B will be less than 6 M. Of course, the concentration of A will
also be greater than before. But as long as we maintain the original temperature,
Keq will stay the same. So when the new equilibrium concentrations are plugged
back into the equilibrium expression, it will still equal . For instance, the new
equilibrium concentrations could be [A] = 3 M, [B] = 4 M, and [C] = 12 M. The
equilibrium concentrations have changed, but the Keq has not.
The Effects of Heat on Equilibrium
Consider this equilibrium equation.