Ostwald’s Isolation method

This method is employed in determining the order of complicated reactions by ‘isolating’ one of the reactants so far as its influence on the rate of reaction is concerned. Suppose the reaction under consideration is :

A+ B+ C ⎯⎯→ products

The order of the reaction with respect to A, Band C is determined. For the determination of the order of reaction with respect to A, Band Care taken in a large excess so that their concentrations are not affected during the reaction. The order of the reaction is then determined by using any of the methods described earlier. Likewise, the order of the reaction with respect to Band C is determined. If n_A , n_B and n_C are the orders of the reaction with respect to A, Band C respectively, the order of the reaction n is given by the expression.

N = n_A + n_B + n_C