Question

When does chemical equilibrium result?

Answer 1

When the forward rate is equivalent to the reverse rate of reaction.

Explanation:

For the equilibrium, `A+BrightleftharpoonsC+D`,

There is a rate forward, `=` `k_f[A][B]`,

And there is a reverse rate, `=` `k_r[C][D]`.

By definition, chemical equilibrium occurs when the forward rate is equivalent to the reverse rate:

`k_f[A][B]` `=` `k_r[C][D]`.

And thus, `([C][D])/([A][B])` `=` `k_f/k_r`

The dimensionless constant, `k_f/k_r`, is also known as `K_c`, the thermodynamic equilibrium constant. This is usually a constant for given conditions.

Large values of `K_c` clearly favour the product sides, whereas small values favour the reactant side. Much thermodynamic data have been recorded with respect to various chemical equilibria.