Which best demonstrates an example of the common ion effect? duction
A The compound CuCl is 500 times less soluble in sea water than it is in
pure water.
ту
B Ammonia is produced commercially when an increase in pressure
shifts the equilibrium toward the product.
ompounds
C A lighted splint goes out in air but bursts into flame when plunged into
pure oxygen.
D The decomposition of carbonic acid in water occurs spontaneously
whereas the combination of carbon dioxide and water does not.

A.  The compound CuCl is 500 times less soluble in sea water than it is in pure water.

pure water.

Explanation:

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.

This principle states that if there is any change in a equilibrium reaction, the equilibrium will shift in a direction so as to minimize the effect.

Thus when a common ion is introduced to an equilibrium reaction, the equilibrium will shift in a direction where the concentration of common ion is decreasing.

When common ion such as from NaCl in sea water is introduced to an equilibrium reaction, the equilibrium will shift in a direction where the concentration of common ion is decreasing i.e. in the left side and thus solubility of CuCl further decreases.