Which of the following salts are insoluble in water?

Solubility rules for inorganic salts dictate that most nitrates and chlorides are soluble in water, while carbonates and phosphates are generally insoluble unless paired with specific cations. According to the rules, all nitrates (NO3-) are soluble, including those of silver and lead [t2][t6]. Most chlorides (Cl-) are soluble, with exceptions like AgCl and PbCl2; however, chlorides of iron (Fe) and manganese (Mn) are soluble [t4][t7]. Conversely, carbonates (CO3 2-) are typically insoluble except when combined with alkali metals or ammonium [t2][t3]. Therefore, Lead (II) carbonate (PbCO3) and Copper (II) carbonate (CuCO3) are insoluble in water [t3]. Phosphates (PO4 3-) follow a similar rule, being insoluble except for those of sodium (Na), potassium (K), and ammonium (NH4), making the salts in option 4 soluble [t3]. Thus, option 3 correctly identifies the insoluble pair.