# What characteristics define a chemical system in equilibrium?

Jul 6, 2016

Equality of forward and reverse rates.

#### Explanation:

For the reaction,

$A + B \rightarrow C + D$;

there is a forward rate, ${K}_{f} \left[A\right] \left[B\right]$; and a reverse rate, ${K}_{r} \left[C\right] \left[D\right]$.

Equilibrium is defined the equality of forward and reverse rates.

i.e. ${K}_{f} \left[A\right] \left[B\right]$$=$${K}_{r} \left[C\right] \left[D\right]$

Or, ${K}_{f} / {K}_{r}$ $=$ $\frac{\left[C\right] \left[D\right]}{\left[A\right] \left[B\right]}$

And ${K}_{f} / {K}_{r}$ $=$ ${K}_{e q}$, $\text{the equilibrium constant}$.