∞ generated and posted on 2016.08.18 ∞
A reversible reaction observed at a point where the overall rate of the forward reaction is occurring at the same overall rate as the reverse reaction.
The important, indeed key thing to keep in mind – other than that this only works with reversible reactions – is that chemical equilibrium mostly does not occur at the point where products and reactants (start and end of forward reactions) are balanced in amount. Instead chemical equilibrium occurs at the balance between amounts and rates. Note that chemical equilibrium is an example of a dynamic equilibrium.
Why is the concept of chemical equilibrium important, for example, to biology? This is because in biology numerous chemical reactions occur that in fact are reversible, but getting these reactions to move in only one rather than the other direction is important. Often this can be accomplished by building up the amount (concentration) of compounds, the reaction of which is desired, so that overall a metabolic pathway tends to move towards the desired product.
Less chemically, the ideas of chemical equilibrium are hugely important to understanding the movement of materials across membranes, and if there is one thing that living things are all about, besides replication, its moving materials across membranes.