# What happens in a dynamic equilibrium exits in a reaction?

Jul 24, 2017

$\text{Option (b) is the answer I would choose.......}$

#### Explanation:

Consider the hypothetical reaction:

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

Now there is a forward rate.......

$\text{Rate forward} = {k}_{f} \left[A\right] \left[B\right]$

And there is a reverse rate.......

$\text{Rate backwards} = {k}_{r} \left[C\right] \left[D\right]$.

The condition of chemical equilibrium does not specify the cessation of chemical change; it does specify equality of FORWARD and REVERSE rates.

$\text{Rate forward"="Rate backward}$, and so.........

${k}_{f} \left[A\right] \left[B\right] \equiv {k}_{r} \left[C\right] \left[D\right]$.......and so......

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

We commonly call the ${k}_{f} / {k}_{r}$ quotient as ${K}_{\text{eq}}$, the  "thermodynamic equilibrium constant", which is usually independent of temperature.