Which of the following compounds has the greatest solubility in water?

• A. AgCl
• B. CaCO_3
• C. NaNO_3
• D. PbSO_4

Answer: (C)

Verified step by step guidance

1. Step 1: Understand that solubility in water depends on the compound's ability to dissociate into ions and the solubility product constant (K\_sp) for sparingly soluble salts. Ionic compounds with high K\_sp values or those that are highly soluble electrolytes dissolve well in water.
2. Step 2: Recognize that NaNO\_3 is a salt of a Group 1 metal (Na\^+) and a nitrate ion (NO\_3\^-), both of which generally form highly soluble compounds in water due to strong ion-dipole interactions and no significant lattice energy barriers.
3. Step 3: Compare the other compounds: AgCl, CaCO\_3, and PbSO\_4 are all sparingly soluble salts with relatively low K\_sp values, meaning they do not dissolve well in water. Their solubility is limited by the equilibrium: \(\mathrm{M}_x\mathrm{A}_y (s) \rightleftharpoons x\mathrm{M}^{n+} (aq) + y\mathrm{A}^{m-} (aq)\), where the product of ion concentrations is constrained by K\_sp.
4. Step 4: Recall that nitrates (NO\_3\^-) are generally soluble with all cations, so NaNO\_3 will dissociate completely in water, unlike the other salts which have low solubility due to their lattice energies and low K\_sp values.
5. Step 5: Conclude that among the given compounds, NaNO\_3 has the greatest solubility in water because it is a soluble ionic salt, while the others are sparingly soluble salts limited by their low K\_sp values.