As an ionic solid dissolves in water, the temperature of the solution increases. What best describes the enthalpy and entropy of the solution?

A. The enthalpy change is negative, and the entropy decreases.
B. The enthalpy change is negative, and the entropy increases.
C. The enthalpy change is positive, and the entropy decreases.
D. The enthalpy change is positive, and the entropy increases.

I think the answer is B or C.

To determine the correct answer, let's analyze the given information. When an ionic solid dissolves in water, it is a process that involves the breaking of ionic bonds in the solid and the formation of new bonds between the ions and water molecules. This process is known as hydration.

Now, let's consider the enthalpy change. Enthalpy is a measure of heat energy, and a negative enthalpy change indicates that heat is released during the process. In this case, the temperature of the solution increases as the ionic solid dissolves, which suggests that heat is being released. Therefore, the enthalpy change is negative.

Next, let's consider the entropy change. Entropy is a measure of disorder or randomness in a system. An increase in entropy usually occurs when particles become more randomly distributed. In the process of dissolving ionic solids in water, the ions from the solid become dispersed and randomly distributed throughout the solution. This dispersal of particles leads to an increase in entropy. Therefore, the entropy change is positive.

Based on our analysis, the correct answer is option D. The enthalpy change is negative (heat is released), and the entropy change is positive (an increase in disorder).

Note: It is important to recognize that there is an exception to this general trend. In cases where the hydration process is highly ordered or the solute and solvent have strong attractive forces, the entropy change may be negative. However, this scenario is not mentioned in the given information, so the general trend applies.