(1) Solubility

Saturated solution: A solution in which the dissolved and undissolved solute are in dynamic equilibrium, or a solution containing the maximum amount of solid under equilibrium conditions.

Solubility: Symbol s, the amount of substance dissolved in unit volume of a saturated solution.

(a) A gas dissolved in a solvent

This is a form of Henry's law which states that for dilute solutions of sparingly soluble gases the concentration in a saturated solution is proportional to the partial pressure of the gas above the solution.

(b) A molecular solid or liquid substance dissolved in a solvent.

The concentration of X in solution is independent of the excess amount of X(s) or X(l) present, and the ratio of [X(s)] or [X(l)] to the standard states of the pure solid or liquid is one (as explained under units of K), and the expression for K is: K = [X(solv)]. In this case K is the solubility of X in the solvent, K = s.

the equilibrium between solid iodine and aqueous iodine

(c) An ionic solid dissolving in water

Solubility constant: Symbol K_s (older term solubility product, symbol K_sp), the equilibrium constant for the dissolution of an ionic compound in water.

(d) Distribution of a solute between two immiscible liquids A and B

Distribution coefficient: The equilibrium for the distribution of a substance between two immiscible liquids (i.e. liquids of low solubility in each other) A and B.

(2) Decomposition of a substance
Example
Decomposition of limestone on heating (calcining).

K = p(CO₂)

 EXERCISES