Question

AgCl is less soluble in NaCl(aq) than in water because

1)of a decrease in Na+ ions.

2)AgCl forms complex ions with NaCl.

3)of a common ion effect.

4)NaCl has a higher solubility product

Answer 1

The reduction is solubility is because 3) of a common ion effect.
The common ion effect is when an ion that is already present in a solution is added, causing the following equilibrium to be disturbed:
AB ↔ [A+] + [B-]

If [B-] is added, then according to Le Chatelier's principle, the equilibrium must shift backward, creating more undissolved precipitate.