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

(N/A) Chemical equilibrium is dynamic in nature. This fact is proven by the synthesis of ammonia using $H_{2}$ and $D_{2}$.
After equilibrium is attained,two mixtures: $(i)$ $H_{2}, N_{2}, NH_{3}$ and $(ii)$ $D_{2}, N_{2}, ND_{3}$ are mixed together and left for a while.
When this mixture is analyzed,it is found that the total concentration of ammonia remains the same as before.
However,when analyzed by a mass spectrometer,it is found that ammonia and all deuterium-containing forms of ammonia $(NH_{3}, NH_{2}D, NHD_{2}, ND_{3})$ as well as dihydrogen and its deuterated forms $(H_{2}, HD, D_{2})$ are present.
This indicates that the scrambling of $H$ and $D$ atoms in the molecules results from the continuation of both forward and reverse reactions.
Thus,the use of the isotope (deuterium) in the formation of ammonia clearly indicates that chemical reactions reach a state of dynamic equilibrium where the rates of forward and reverse reactions are equal,and there is no net change in composition.