Among the given compounds, PbCl2 is more soluble in an acidic solution than in a neutral solution.
PbCl2 is a sparingly soluble salt, and its solubility decreases as the pH of the solution increases from acidic to neutral or basic. This is because in acidic solution, the H+ ions from the acid react with the Cl- ions from the salt to form HCl, which is a strong electrolyte and increases the solubility of PbCl2 due to the common ion effect. In contrast, in a neutral solution, there are no H+ ions to react with the Cl- ions from the salt, resulting in a lower solubility of PbCl2.
CaF2, AgBr, and HgI2 are not affected by pH changes in the same way as PbCl2. Therefore, their solubility in acidic and neutral solutions remains the same.