Question

What is dynamic equilibrium?

Answer 1

A state of equilibrium in which the forward and backward reactions are occurring at the same rate with no net change.

Explanation:

To illustrate dynamic equilibrium, let's take a look at this reaction:

`N_2(g) + 3H_2(g) rightleftharpoons 2NH_3(g)`

In this reaction, nitrogen gas and hydrogen gas are in a dynamic equilibrium with ammonia gas.

• When `N_2` and `H_2` are first placed into a reaction vessel, they will begin to react to form `NH_3`. The rate of the forward reaction, `N_2(g) + 3H_2(g) -> 2NH_3(g)`, is high.
• However, eventually, `NH_3` will start to reform `N_2` and `H_2`.
  The rate of the backward reaction, `2NH_3(g) -> N_2(g) + 3H_2(g)`, begins to rise.
• Eventually, the rates of the two reactions will be the same. Equilibrium has been reached.

We should remember, though, that this is a dynamic equilibrium!

This means that, although it may seem like nothing is happening (because the concentrations of the reactants and products essentially stay constant), `N_2` and `H_2` are still constantly forming `NH_3`. `NH_3` is also constantly reforming into `N_2` and `H_2`.
It's just that the rates at which they do this are the same.

So, although reactions are occurring, there is no net change.