Final answer:
Benzoic acid is expected to be more soluble in water than 9-fluorenone due to its polar carboxylic acid group, which forms stronger intermolecular forces with water.
Step-by-step explanation:
Predicting the solubility of compounds in water involves considering their molecular structure and the types of intermolecular forces present. In the comparison between benzoic acid and 9-fluorenone, we look at the structures of both compounds. Benzoic acid has a polar carboxylic acid group attached to a nonpolar benzene ring, which provides it with the ability to form hydrogen bonds with water, enhancing its solubility. On the other hand, 9-fluorenone is also an aromatic ketone but does not have the polar carboxylic acid group; hence, it would likely have weaker interactions with water molecules compared to benzoic acid. Therefore, we can predict that benzoic acid will be more soluble in water than 9-fluorenone due to its ability to participate in stronger intermolecular forces with water.