Page 4 - Pharmaceutical analytical chemistry |

Bases example: hydroxides of the alkali and alkaline earth metals such
as NaOH, KOH, Ca(OH)2.
Salts example: most salts such as sodium chloride, potassium iodide
etc….
Strong electrolytes share the common characteristic of ionizing
completely when dissolved in water:
HCl (aq) ⎯⎯→ H+ (aq) + Cl- (aq)
Weak electrolytes:

A weak electrolyte is an electrolyte that dissolves in H2O to give a
relatively small percentage of ions. They are generally molecular
substances, e.g. NH3. Pure ammonia is a gas that readily dissolves in
water and goes into solution as ammonia molecules NH3 (aq). The latter
react with water to form NH4+ & OH- ions.

NH3 (aq) + H2O (l) ⎯→ NH4+ (aq) + OH- (aq)

Both NH4+ & OH- ions react with each other to give back NH3 &
H2O molecules.

NH4+ (aq) + OH- (aq) ⎯→ NH3 (aq) + H2O (l)

Both reactions, the original (forward) and its reverse, occur
constantly and simultaneously.

 NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)

From these reactions, just a small % of NH3 molecules ( 3%) has
reacted at any given moment to form ions. Thus, NH3 is a weak
electrolyte.

3