Final answer:
The term for the suppression of ionization of a weak electrolyte when one of its ions is added from another source is the common ion effect. The common ion effect is explained by Le Chatelier's principle, as the system adjusts to minimize the impact of the added ion, shifting the equilibrium.
Step-by-step explanation:
When a solution of a weak electrolyte is altered by adding one of its ions from another source, the ionization of the weak electrolyte is suppressed. This behavior is termed the common ion effect.
The common ion effect is a shift in equilibrium that occurs when a strong electrolyte containing one ion in common with a reaction system that is at equilibrium is added to the system. It causes a decrease in the solubility of an ionic species or a decrease in the ionization of a weak acid or base. This is due to Le Chatelier's principle, which states that the system will adjust to counteract the change introduced by the added common ion.
For example, if acetic acid is in equilibrium in a solution and we add sodium acetate, which also provides acetate ions, the additional acetate ions will suppress further dissociation of acetic acid, shifting the equilibrium to the left. Similarly, adding iodide ions to a solution at equilibrium with silver iodide will result in the precipitation of AgI and lower concentrations of dissolved Ag+ and I- ions, as less AgI may be dissolved in the presence of a common ion.