Consider synthesis of Ammonia by Haber's process :

First the concentration of hydrogen and concentration of nitrogen decreases with time and concentration of product increases with time and after a certain time the composition of mixture remains the same even though some of the reactants are still present. This indicates the reaction has reached equilibrium. Chemical reactions reach a state of dynamic equilibrium in which the rates of forward and reverse reactions are equal and there is no net change in composition. This can be explained by the use of deuterium isotope in the formation of ammonia, in place of H2, where ND3 is formed. After equilibrium is attained, the two mixtures namely H2 hydrogen, N2 nitrogen, NH3 ammonia are mixed together and left for a while. Later, when this mixture is analysed, it is found that the concentration of ammonia is just the same as before.

However, when this mixture is anlaysed by a mass spectrometer it is found that ammonia and all deuterium containing forms of ammonia, NH3, NH2D, NHD2 and ND3 and dihydrogen and its deuterated forms H2, HD and D2 are present. Thus we can conclude that moving Hhydrogen and Ddeuterium atoms in the molecules must result continuation of forward and reverse reaction in the mixture. If the reaction had simply stopped when equilibrium is reached, then there would have been no mixing of isotopes in this way. Equilibrium can be attained from both sides, whether we start reaction by taking H2 gas. Let us observe this by taking other example of formation of HI g or decomposition of HI in to H2 and I2.

ที่มา : http://www.7active.in

ลิงค์ : http://youtu.be/MVjItVOuq-A

อัพโหลดโดย : 7activestudio