Nernst's Distribution Law

Nernst's Distribution Law

Nernst's Distribution Law

When a solute distribute itself between two immiscible solvents in equilibrium, then the ratio of its concentration in two solvents remains constant. This is called Distribution law.

Example: The solute iodine distributes itself in CCl4 and water solvents. Let C1 and C2 be the concentration of I2 in CCl4 and water respectively. Then from Distribution law-
C1 / C2 = KD
where KD is partition coefficient.
The value of KD depends upon the Temperature, Nature of solute, Nature of two solvents and Manner in which the constant is expressed
i.e. C1 / C2 or C2 / C1

Essential Conditions for the Distribution Law

Followings are the essential conditions for that-
1. Temperature must be constant.
2. Solutions are must be dilute.
3. Two solutions should be insoluble or very sparingly soluble and their solubility should not be affected by the presence of solute.
4. Solute must not be undergo dissociation or association or interaction with any of the solvents.

Thermodynamic Derivation of the Distribution Law

Distribution Law B.Sc. 2nd Year Notes