Question

What does an equilibrium constant tell us?

Answer 1

1. Equilibrium is a state where the rate of the forward reaction is equal to the rate of the backward reaction.
2. The reaction which proceeds in both directions is called a reversible reaction.
3. In an equilibrium state the reactant and product concentration both are constant.
4. Therefore, an equilibrium constant is needed to identify the ratio of active product masses over active reactant masses.
5. Let us take an exemplary reaction:
   $\mathrm{aA}+\mathrm{bB}\rightleftharpoons \mathrm{cC}+\mathrm{dD}$
6. The equilibrium constant for the following reaction is:
   ${\mathrm{K}}_{\mathrm{c}}=\frac{{\left[\mathrm{C}\right]}^{\mathrm{c}}{\left[\mathrm{D}\right]}^{\mathrm{d}}}{{\left[\mathrm{A}\right]}^{\mathrm{a}}{\left[\mathrm{B}\right]}^{\mathrm{b}}}$
7. Where ${\mathrm{K}}_{\mathrm{c}}$ is the equilibrium constant, $\left[\mathrm{C}\right]\mathrm{and}\left[\mathrm{D}\right]$ are the concentration of products, c and d are the stoichiometric powers of products concentration, similarly $\left[\mathrm{A}\right]\mathrm{and}\left[\mathrm{B}\right]$ are the concentration of reactants, a and b are the stoichiometric powers of reactants concentration.
8. This signifies that the equilibrium constant is useful in determining the concentration of reactant and product, i.e. whether the concentration of reactant or product is higher.