Which of the following salts would become more soluble in water as the temperature decreases?

• A. CaCl2
• B. NaCl
• C. Ce2(SO4)3
• D. KNO3

Answer: (C)

Verified step by step guidance

1. Understand the concept of solubility and its temperature dependence: Most salts increase in solubility as temperature increases, but some salts have solubility that decreases with increasing temperature, meaning they become more soluble as temperature decreases.
2. Recall that salts with exothermic dissolution processes tend to become more soluble at lower temperatures because dissolving them releases heat, so lowering temperature favors dissolution according to Le Chatelier's principle.
3. Analyze each salt given: CaCl2, NaCl, Ce2(SO4)3, and KNO3. Commonly, KNO3 and NaCl have solubility that increases with temperature, while Ce2(SO4)3 is known to have solubility that decreases as temperature rises.
4. Use the principle that if a salt's dissolution is exothermic, lowering temperature shifts equilibrium toward more dissolved ions, increasing solubility; thus, Ce2(SO4)3 fits this behavior.
5. Conclude that among the options, Ce2(SO4)3 is the salt that becomes more soluble in water as temperature decreases due to its exothermic dissolution.