Answer to Question #128677 in Physical Chemistry for Muhammad Nabeel

Question

(a) Elaborate how solutions are equilibrated mixtures. Prove mathematically that there is equilibrium in the solution in terms of its concentration.
(b) Explain why supersaturated solutions are unstable solutions and change to saturated solutions upon lowering the temperature.

Answer 1

(a) In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. This state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but equal. Thus, there are no net changes in the concentrations of the reactants and products. Such a state is known as dynamic equilibrium.

(b)Because the solubility of most solids increases with increasing temperature, a saturated solution that was prepared at a higher temperature usually contains more dissolved solute than it would contain at a lower temperature. ... Like a supercooled or superheated liquid, a supersaturated solution is unstable.