Page 6 - Microsoft Word - Equilibrium State key notes

 The degree of ionization and its dependence on concentration and common
ion are discussed.

 Common ion Effect: The shift in equilibrium position caused by the addition or
presence of an ion involved in the equilibrium reaction is known as common
ion effect

 Strength of acid or base is determined with the help of extent of ionization in
aqueous solution.
 The pH scale (pH = -log[H+]) for the hydrogen ion concentration (activity) has
been introduced and extended to other quantities (pOH = – log[OH–]) ; pKa =
–log[Ka] ;pKb = –log[Kb]; and pKw = –log[Kw] etc.).

 The ionization of water has been considered and we note that the equation:
pH +pOH = pKw is always satisfied. The salts of strong acid and weak base,
weak acid and strong base, and weak acid and weak base undergo hydrolysis
in aqueous solution.

 Buffer solutions: are the solutions which resist change in pH on dilution or
addition of small amount of acid or alkali.

 Acidic buffers contain equimolar quantities of a weak acid and one of its salt
with a strong base.
 Basic buffers contain equimolar quantities of a weak base and one of its salt
with a strong acid.

 The solubility equilibrium of sparingly soluble salts is discussed and the
equilibrium constant is introduced as solubility product constant (Ksp). Its
relationship with solubility of the salt is established. Under equilibrium
conditions, Ksp = Qsp The solubility of salts of weak acids, like phospates,
increases with decrease in pH. The conditions of precipitation of the salt from
their solutions or their dissolution in water are worked out.