How does one predict, whether a particular reaction goes to completion or to an equilibrium mixture?
It is evident from the above that thermodynamic quantities such as and K do not indicate whether or not a reaction goes to completion, is fast or is slow etc… They do give an idea of how the degree of conversion can be optimized or, after possible stimulation, can be made self-sustaining. The relationship between the degree of conversion of a reaction and the K-value depends upon the initial composition. In addition, the expression for the equilibrium constant, K is also important. Notwithstanding this, the table below can be used in a qualitative manner to relate and K to the likely type of reaction. BEWARE It is not possible to predict kinetic behaviour on the basis of such thermodynamic data. Thus at room temperature the NO2-dimerization is not only self-sustaining, but the reaction starts spontaneously. On the other hand, N2 and H2 do not react at room temperature, requiring a high temperature even in the presence of a catalyst to start the reaction even though the -value for the
