Question

Explain the dynamic nature of chemical equilibrium with a suitable example.

Answer 1

Dynamic nature of chemical equilibrium:

1. Consider a chemical reaction: A ⇌ B.
   K_C = [B]/[A]
   At equilibrium, the ratio of the concentration of the product to that of the concentration of the reactant is constant and this is equal to K_C.
2. At this stage reaction takes place in both directions at the same speed although the reaction appears to have stopped. Thus, chemical equilibrium is dynamic in nature. Dynamic means moving and at a microscopic level, the system is in motion.
3. For example, in the reaction between H₂ and I₂ to form H_I, the colour of the reaction mixture becomes constant because the concentrations of H₂, I₂ and H_I become constant at equilibrium.
   \[\ce{H2 + I2 ⇌ 2HI}\]
   Thus, when equilibrium is reached, the reaction appears to have stopped. However, this is not the case. The reaction is still going on in the forward and backward direction but the rate of forwarding reaction is equal to the rate of backward reaction. Hence, chemical equilibrium is dynamic in nature and not static.