For most substances the solubility increases as the temperature, which one of these substances exhibits a decrease in solubility with an increase in Temperature?
a. NaNO3
b. CaCl2
c. NaCl
d.Ce2(SO4)3
The Correct Answer and Explanation is :
The correct answer is d. Ce2(SO4)3 (Cerium(III) sulfate).
Explanation:
For most solutes, the solubility in water generally increases as the temperature rises. However, there are exceptions to this rule. One such exception is Cerium(III) sulfate (Ce2(SO4)3), which exhibits a decrease in solubility as the temperature increases. This behavior is typically observed with salts that are exothermic in their dissolution process. In simpler terms, when these salts dissolve, they release heat, and the process becomes less favorable at higher temperatures, causing their solubility to decrease.
The solubility of salts is influenced by the balance between the dissolution process (which often absorbs energy) and the hydration of ions (which typically releases energy). For most salts, the dissolution process is endothermic, meaning that as temperature increases, the dissolution becomes more favorable. However, when the dissolution of a substance is exothermic, the increase in temperature can push the system away from equilibrium, thus reducing its solubility.
Why the other substances don’t fit:
- NaNO3 (Sodium nitrate): The solubility of NaNO3 increases significantly with temperature, which is typical for many ionic salts. NaNO3 dissolves endothermically, so raising the temperature makes the dissolution process more favorable.
- CaCl2 (Calcium chloride): This salt also dissolves exothermically, releasing heat when it dissolves in water. However, despite being exothermic, its solubility increases with increasing temperature because the ionic lattice of CaCl2 is very weak, making it easier to dissociate as the temperature rises.
- NaCl (Sodium chloride): Sodium chloride is another example of a salt whose solubility increases slightly with temperature. However, the change is not as pronounced as other substances, and it remains endothermic.
For Ce2(SO4)3, due to its exothermic dissolution nature, its solubility decreases with an increase in temperature, making it a unique case.
I will now generate an image to visually represent this concept.
Here is a visual representation of the solubility trends for the substances you asked about. As you can see, the solubility of NaNO3, CaCl2, and NaCl increases with temperature, while Ce2(SO4)3 shows a decrease in solubility as the temperature rises, illustrating the unique behavior of Cerium(III) sulfate.