What is the Difference Between Job’s Method and Mole Ratio Method?

🆚 Go to Comparative Table 🆚

The key difference between Job's method and the mole ratio method lies in the way the molar concentrations of reactants are held constant during the experiment.

In Job's method:

  • The molar concentrations of all reactants are held constant.
  • This method is used to determine the stoichiometry of a binding event.
  • It is named after the scientist Paul Job, who developed the technique in 1928.

In mole ratio method:

  • The molar concentration of one reactant is kept constant, while the molar concentration of the other reactant varies.
  • This method is an alternative to Job's method and is also used to determine stoichiometry.
  • It is particularly useful for determining the stoichiometry of metal-ligand complexes.

Both methods are used in analytical chemistry to determine the stoichiometry of various reactions, but they are applied in different contexts and with different experimental setups.

Comparative Table: Job’s Method vs Mole Ratio Method

The key difference between Job's method and mole ratio method lies in the way they determine the stoichiometry of a binding event:

Job's Method Mole Ratio Method
Involves preparing a series of solutions with constant total moles of reactants ntotal (nM + nL) Involves preparing a series of solutions with constant molar concentration of one reactant
Mole fractions of ligand and metal are used to express their relative amounts The molar ratio of reactants is used to determine the stoichiometry
Stoichiometry can be determined by knowing the ratio of reactants in the solution Stoichiometry is deduced by keeping the molar concentration of one reactant constant and varying the concentration of the other reactant
Suitable for determining the composition of complex ions Suitable for determining the stoichiometry in chemical reactions

Job's method, also known as the method of continuous variations, is used to determine the stoichiometry of a metal-ligand complex by preparing a series of solutions with constant total moles of reactants. On the other hand, the mole ratio method is an alternative method to Job's method, where the molar concentration of one reactant is kept constant, and the molar concentration of the other reactant is varied to determine the stoichiometry.