the reverse reaction, Fig. . Attainment of chemical equilibrium. Eventually, the two reactions occur at the same rate and the system reaches a state of equilibrium.
Similarly, the reaction can reach the state of equilibrium even if we start with only C and D; that is, no A and B being present initially, as the equilibrium can be reached from either direction. The dynamic nature of chemical equilibrium can be demonstrated in the synthesis of ammonia by Haber’s process. In a series of experiments, Haber started with known amounts of dinitrogen and dihydrogen maintained at high temperature and pressure and at regular intervals determined the amount of ammonia present. He was successful in determining also the concentration of unreacted dihydrogen and dinitrogen.
Fig. . (page ) shows that after a certain time the composition of the mixture remains the same even though some of the reactants are still present. This constancy in composition indicates that the reaction has reached equilibrium.
In order to understand the dynamic nature of the reaction, synthesis of ammonia is carried out with exactly the same starting conditions (of partial pressure and temperature) but using D (deuterium) in place of H . The reaction mixtures starting either with H or D reach equilibrium with the same composition, except that D and ND are present instead of H and NH . After Dynamic Equilibrium – A Student’s Activity Equilibrium whether in a physical or in a chemical system, is always of dynamic nature. This can be demonstrated by the use of radioactive isotopes.
This is not feasible in a school laboratory. However this concept can be easily comprehended by performing the following activity. The activity can be performed in a group of or students. Take two 100mL measuring cylinders (marked as and ) and two glass tubes each of cm length.
Diameter of the tubes may be same or different in the range of -5mm. Fill nearly half of the measuring cylinder- with coloured water (for this purpose add a crystal of potassium permanganate