\(\mathrm{KBr}\) is relatively soluble in water, yet its enthalpy of solution is \(+19.8 \mathrm{kJ} / \mathrm{mol} .\) Which of the following statements provides the best explanation for this behavior? (a) Potassium salts are always soluble in water. (b) The entropy of mixing must be unfavorable. (c) The enthalpy of mixing must be small compared to the enthalpies for breaking up water-water interactions and K-Brionic interactions. (d) KBr has a high molar mass compared to other salts like NaCl.

Potassium salts are always soluble in water. This statement does not provide any explanation for the enthalpy of solution being positive (+19.8 kJ/mol). It only states KBr's solubility properties.

The entropy of mixing must be unfavorable. Entropy is a measure of disorder in a system. The dissolution process generally results in an increase in the disorder of the system due to mixing. This statement is contradictory since KBr is soluble in water, which indicates that the entropy of mixing must be favorable, not unfavorable.

The enthalpy of mixing must be small compared to the enthalpies for breaking up water-water interactions and K-Br ionic interactions. Enthalpy of solution is the sum of: 1. Enthalpy for breaking up water-water interactions (enthalpy of hydration for water). 2. Enthalpy for breaking up K-Br ionic interactions (lattice enthalpy). 3. Enthalpy for forming new interactions between water molecules and solute ions (enthalpy of hydration for solute ions). A positive enthalpy of solution means that the process is endothermic, which means it absorbs energy from its surroundings. This statement suggests that the favorable enthalpy of mixing is relatively small compared to the endothermic processes of breaking up water-water and K-Br ionic interactions. Therefore, the overall enthalpy of solution is positive. This statement provides a reasonable explanation for the behavior of KBr with a positive enthalpy of solution.

KBr has a high molar mass compared to other salts like NaCl. This statement doesn't directly explain the connection between KBr's solubility in water and its positive enthalpy of solution. Molar mass doesn't necessarily correlate with solubility or enthalpy of solution.

The best explanation for KBr's behavior with positive enthalpy of solution while being soluble in water is given by statement (c): The enthalpy of mixing must be small compared to the enthalpies for breaking up water-water interactions and K-Br ionic interactions.