Which factor generally increases the solubility of sparingly soluble salts?

Which factor generally increases the solubility of sparingly soluble salts?

• A. Lowering temperature
• B. Increasing temperature (endothermic dissolution)
• C. Adding a common ion
• D. Adding a strong acid to form a more soluble species

Answer: (C)

Solubility of sparingly soluble salts is governed by the dissolution equilibrium: solid ⇌ ions in solution. The effect of temperature on this equilibrium depends on whether the dissolution process is endothermic or exothermic. For many sparingly soluble salts, dissolving absorbs heat (endothermic), so raising the temperature supplies the energy the process needs and shifts the equilibrium toward more dissolved ions. That means solubility generally increases with temperature for those salts. Conversely, lowering the temperature would often decrease solubility in the same cases. Adding a common ion to the solution, on the other hand, pushes the equilibrium toward the solid due to Le Chatelier’s principle, which decreases solubility rather than increases it. So that factor does not generally make sparingly soluble salts more soluble. Adding acid can sometimes increase solubility by transforming a poorly soluble species into a more soluble form, but that effect depends on the specific salt and isn’t universal. In short, the most general factor that increases solubility for many sparingly soluble salts is increasing temperature when the dissolution is endothermic.

Solubility of sparingly soluble salts is governed by the dissolution equilibrium: solid ⇌ ions in solution. The effect of temperature on this equilibrium depends on whether the dissolution process is endothermic or exothermic. For many sparingly soluble salts, dissolving absorbs heat (endothermic), so raising the temperature supplies the energy the process needs and shifts the equilibrium toward more dissolved ions. That means solubility generally increases with temperature for those salts. Conversely, lowering the temperature would often decrease solubility in the same cases.

Adding a common ion to the solution, on the other hand, pushes the equilibrium toward the solid due to Le Chatelier’s principle, which decreases solubility rather than increases it. So that factor does not generally make sparingly soluble salts more soluble. Adding acid can sometimes increase solubility by transforming a poorly soluble species into a more soluble form, but that effect depends on the specific salt and isn’t universal.

In short, the most general factor that increases solubility for many sparingly soluble salts is increasing temperature when the dissolution is endothermic.