Chemical Equilibrium: A Dynamic Condition

  -Equilibrium is not static but it is a highly dynamic situation.

-A double arrow () is used to show that a reaction is occurring in both directions.

-Why does equilibrium occur? The forward rate and the reverse rate become the same.

Analogy: two island cities connected by a single bridge. Suppose traffic flow on the bridge is the same in both directions. It is obvious that there is motion, but the number of cars in each city does not change because there is an equal flow of cars entering and leaving. The result is no net change in the number of cars in each of the two cities.

-The more collisions, the faster the reaction. This is why speed of a reaction depends on concentrations.

-When the concentrations of reactants reach levels at which the rate of the forward reaction equals the rate of the reverse reaction, the system has reached equilibrium.