Explain Job's method for determination of composition of complex with the help of suitable example.

Answer 1

Job's method, also known as the continuous variation method, is a technique used in the determination of the stoichiometry of a complex formed between two or more reactants. The method involves varying the ratio of the reactants in a series of solutions and measuring the resulting effect on a property of the complex.

For example, let's consider the formation of a complex between a metal ion M and a ligand L. The complex formed can be represented as MLn, where n is the stoichiometry of the complex. To determine the value of n, we can mix solutions of M and L in different mole ratios and measure a property of the resulting complex, such as the absorbance of a solution at a specific wavelength.

By varying the mole ratio of M and L in the solutions and measuring the absorbance of the resulting complexes, we can construct a Job's plot, which is a plot of the absorbance of the complex against the mole fraction of one of the reactants. The point on the plot where the absorbance is maximized corresponds to the mole fraction where the complex is formed in the desired stoichiometry.

By using the Job's method, we can determine the stoichiometry of the complex formed between the metal ion and the ligand, providing valuable information about the composition of the complex and the nature of the interactions between the reactants.