Final answer:
AgCl (Silver Chloride) is the ionic compound among the options given that is not soluble in water, according to solubility rules that state chlorides of Ag+, Pb2+, and Hg22+ are insoluble.
Step-by-step explanation:
Among the listed options, the ionic compound that is not soluble in water is AgCl (Silver Chloride). Sodium chloride (NaCl), ammonium sulfate ((NH4)2SO4), calcium acetate (Ca(CH3CO2)2), and calcium chloride (CaCl2) are soluble in water. These solubilities are explained by general solubility rules, which state that salts containing Group 1 elements and NH4+ are soluble, and that most acetates and chlorides are soluble, with the important exception of chlorides of Ag+, Pb2+, and (Hg2)22+. Thus, while NaCl, (NH4)2SO4, Ca(CH3CO2)2, and CaCl2 dissolve in water, AgCl remains largely insoluble.