# What is the equilibrium constant formula?

May 9, 2017

${K}_{\text{eq}} = \frac{\left[A\right] \left[B\right]}{\left[C\right] \left[D\right]}$

#### Explanation:

And this describes the equilibrium reaction:

$A + B r i g h t \le f t h a r p \infty n s C + D$

For the derivation, which depends on equality of $\text{the rate forwards}$ with respect to the $\text{rates backwards}$, see this old answer. Note that ${K}_{\text{eq}}$ must be measured, and it has been measured for a variety of reactions.