Reversible Chemical Reactions
Not all reactions go to completion...Equilibrium 1
The graphical way of looking at equilibrium
As a system approaches equilibrium, both the forward and reverse reactions are occurring.
At equilibrium, the forward and reverse reactions are proceeding at the
Once equilibrium is achieved, the amount of each reactant and product remains constant.
Equilibrium can be approached from either side of the reaction
An analogy of equilibrium
And another analogy
The equilibrium constant, K
First of all, notice that the equilibrium constant is an upper-case K while the rate constant, k, is lower-case. The two k's are related however! If the rates of the forward and reverse reactions are the same, then rate of forward = rate of reverse and K is kf/kr.
From our study of kinetics, we know that rate and the rate constant are not the same (unless it is a zero order reaction).
The magnitude of K tells us if one direction is favored over the other.
The general equilibrium expression
What is Q?
Pure solids and liquids do not have a "concentration" so these are left out of equilibrium expressions. Reactions with mixed phases are referred to as heterogeneous and reactions with uniform phases across reactants and products are homogeneous.