Chemical equilibrium

Chemical equilibrium refers to where the forward and backward reactions are both occurring at an equal rate. This only occurs in a closed system, and the concentration of reactants and products remain constant at equilibrium. Both sides are the rate-determining steps of each other.

$$aA+bB\rightleftharpoons cC+dD$$

We can only have gaseous or aqueous states in the equilibrium expression.

Applications

The principle of chemical equilibrium has a few industrial applications:

• Haber process, $\Delta H=-93kJ\cdot {\text{mol}}^{-1}$

$$N_{2(g)}+3H_{2(g)}\rightleftharpoons 2N{H}_{3(g)}$$

• Contact process

$$2S{O}_{2(g)}+O_{2(g)}\rightleftharpoons 2S{O}_{3(g)}$$

• Production of methanol

$$C{O}_{(g)}+2H_{2(g)}\rightleftharpoons C{H}_{3}O{H}_{(g)}$$

See also

• Le Châtelier’s principle