# What is dynamic equilibrium?

May 2, 2018

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:

${N}_{2} \left(g\right) + 3 {H}_{2} \left(g\right) r i g h t \le f t h a r p \infty n s 2 N {H}_{3} \left(g\right)$

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 $N {H}_{3}$. The rate of the forward reaction, ${N}_{2} \left(g\right) + 3 {H}_{2} \left(g\right) \to 2 N {H}_{3} \left(g\right)$, is high.
• However, eventually, $N {H}_{3}$ will start to reform ${N}_{2}$ and ${H}_{2}$.
The rate of the backward reaction, $2 N {H}_{3} \left(g\right) \to {N}_{2} \left(g\right) + 3 {H}_{2} \left(g\right)$, 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 $N {H}_{3}$. $N {H}_{3}$ 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.