Which of the following compounds would be expected to be the most soluble in water?

• A. NaNO_3
• B. PbBr_2
• C. BaSO_4
• D. AgCl

Answer: (A)

Verified step by step guidance

1. Step 1: Understand that solubility in water depends largely on the compound's ability to dissociate into ions and the strength of the ionic bonds, as well as lattice energy and hydration energy.
2. Step 2: Recognize that compounds containing alkali metal ions (like Na\+) and nitrate ions (NO_3\-) are generally very soluble in water due to their strong hydration and low lattice energy.
3. Step 3: Consider the other compounds: PbBr_2, BaSO_4, and AgCl are all salts with ions that tend to form less soluble compounds because of higher lattice energies and lower hydration energies.
4. Step 4: Recall the solubility rules: nitrates (NO_3\-) are almost always soluble, while sulfates (SO_4^{2-}), bromides (Br^-), and chlorides (Cl^-) have varying solubilities depending on the cation, with Pb^{2+}, Ba^{2+}, and Ag^+ often forming sparingly soluble salts.
5. Step 5: Conclude that NaNO_3 is expected to be the most soluble in water among the given options because it contains the nitrate ion and an alkali metal cation, both of which favor high solubility.