Why concentrations of pure solids and liquids taken to be Unity in case of equilibrium constant?

Open in App

Solution

Concentration is nothing but active mass.
Molar concentration is directly proportional to density. Over the course of a reaction the density of a solid or liquid reactant doesn't change . The mass and volume changes, but the ratio of the two is constant. As density of solid or liquid remains constant, the active mass is taken as 1 . Gases occupy the volume of their container, and if some gases are removed, concentration gets changed.

Always equilibrium constant K is the ratio of the concentration of product to the reactant. For solids and liquids the active mass is unity. As in the LHS side no other term is there.

Suggest Corrections

Similar questions

Q. Assertion :The active mass of pure solid and pure liquid is taken unity. Reason: The active mass of pure solids and liquids depends on the density and molecular mass. The density and molecular of a mass of pure liquids and solids are constant.

Q. Assertion :Pure liquids and solids can be ignored while writing the equilibrium constant expression for heterogeneous equilibria. Reason: The concentration of pure liquids and solids does not remain constant.

Q. Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

Q. Concentration of pure solid and liquid is not included in the expression of equilibrium constant because:

The active masses of pure solid or liquid phasesare not included in theexpression of equilibrium constant as:
a)solid and liquid concentrations are independent of their quantities
b)solids and liquids react very slowly
c)solids and liquids at equilibrium do not interact with gaseous phase

d)the molecules of solids and liquids do not migrate to the gaseous phase

Join BYJU'S Learning Program