Which of the following ionic compounds is soluble in water?

• A. BaSO_4
• B. PbSO_4
• C. AgCl
• D. NaNO_3

Answer: (D)

Verified step by step guidance

1. Understand the concept of solubility: Solubility in water depends on the ability of the ionic compound to dissociate into its ions and interact favorably with water molecules. Generally, compounds containing alkali metal ions (like Na\+) and nitrate ions (NO_3\-) are highly soluble in water.
2. Recall common solubility rules: For sulfates (SO_4^{2-}), most are soluble except those with Ba^{2+}, Pb^{2+}, and a few others, which are generally insoluble or sparingly soluble. For chlorides (Cl^-), most are soluble except those with Ag^+, Pb^{2+}, and Hg_2^{2+}.
3. Analyze each compound given: BaSO_4 and PbSO_4 are sulfates with Ba^{2+} and Pb^{2+}, which are exceptions to sulfate solubility and thus are not very soluble. AgCl contains Ag^+, which forms an insoluble chloride.
4. Compare with NaNO_3: Sodium nitrate contains Na^+ (an alkali metal ion) and NO_3^- (nitrate ion), both of which form compounds that are generally soluble in water without exceptions.
5. Conclude that among the options, NaNO_3 is soluble in water because it follows the solubility rules for alkali metal nitrates, while BaSO_4, PbSO_4, and AgCl are not soluble due to their respective ions causing low solubility.