Which of the following statements about the common ion effect are true? a. If we add ammonium chloride to a solution of ammonia, the concentration of the [H3O+] in solution will increase.
b. If we add potassium perchlorate to a solution of perchloric acid, the concentration of the [H3O+ ] in solution will noticeably decrease.
c. A solution composed of 1.0 M nitric acid and 1.0 M sodium nitrate will have approximately the same pH as a 1.0 M solution of nitric acid.
d. The mixture of a weak acid and the salt of its conjugate base will have a lower pH than the same concentration of the weak acid by itself.
e. The mixture of a weak base and the salt of its conjugate acid will have a higher pH than the same concentration of the weak base by itself.
f. If we add potassium acetate to a solution of acetic acid, the concentration of the [H3O+ ] in solution will decrease.

c. A solution composed of 1.0 M nitric acid and 1.0 M sodium nitrate will have approximately the same pH as a 1.0 M solution of nitric acid.

f. If we add potassium acetate to a solution of acetic acid, the concentration of the [H3O+ ] in solution will decrease.

Explanation:

The common-ion effect describes the effect on an equilibrium involving a substance that adds a common ion (an ion that is already part of the equilibrium) to the solution.

Addition of a common ion decreases the ionization of weak acids and bases. It also decreases the solubility of the common ion.

a. If we add ammonium chloride to a solution of ammonia, the concentration of the [H3O+] in solution will increase.

False: H₃O⁺ ion is not part of the equilibrium

b. If we add potassium perchlorate to a solution of perchloric acid, the concentration of the [H3O+ ] in solution will noticeably decrease.

False: Addition of potassium perchlorate, a neutral salt will have no effect on the ionization of perchloric acid as it is a strong acid. The concentration of H₃O⁺ ion in solution will stay the same.

c. A solution composed of 1.0 M nitric acid and 1.0 M sodium nitrate will have approximately the same pH as a 1.0 M solution of nitric acid.

True: Addition of sodium nitrate, a neutral salt will have no effect on the ionization of nitric acid as it is a strong acid. The concentration of H₃O⁺ ion in solution will stay the same.

d. The mixture of a weak acid and the salt of its conjugate base will have a lower pH than the same concentration of the weak acid by itself.

False: The common ion will result in less ionization of the weak acid. Thus pH of the resulting solution will be higher than the weak acid alone.

e. The mixture of a weak base and the salt of its conjugate acid will have a higher pH than the same concentration of the weak base by itself.

False: The common ion will result in less ionization of the weak base. Thus pH of the resulting solution will be lower than the weak base alone.

f. If we add potassium acetate to a solution of acetic acid, the concentration of the [H3O+ ] in solution will decrease.

True: When potassium acetate is added to an acetic acid system at equilibrium, the presence of the common ion acetate, will result in less ionization of acetic acid, therefore,, the pH of the solution will increase.