When calcium chloride \(\left(\mathrm{CaCl}_{2}\right)\) dissolves in water, the temperature of the water increases dramatically. Which of the following must be true regarding the enthalpy of solution? (A) The lattice energy in \(\mathrm{CaCl}_{2}\) exceeds the bond energy within the water molecules. (B) The hydration energy between the water molecules and the solute ions exceeds the lattice energy within \(\mathrm{CaCl}_{2}\) . (C) The strength of the intermolecular forces between the solute ions and the dipoles on the water molecules must exceed the hydration energy. (D) The hydration energy must exceed the strength of the intermolecular forces between the water molecules.

In a solution process, there are two principal types of energy changes: lattice energy, which is the energy required to separate a mole of a solid ionic compound into its gaseous ions, and hydration energy, the energy released when new bonds are made between the ions and water molecules.

Option (A) talks about lattice energy exceeding the bond energy within water molecules but we are interested in the exchange between the solute and the solvent not within the solvent itself, hence discard this option. Option (B) suggests that the hydration energy (energy released due to interaction of water with solute ions) is greater than the lattice energy (energy used to break the solid solute into ions); which falls in line with our concept of an exothermic solution process. Thus this seems a reasonable choice. Option (C) refers to the strength of intermolecular forces between the solute ions and the dipoles on the water molecules exceeding the hydration energy; but in reality, it's the hydration energy that corresponds to these forces, hence discard this. Option (D) relates the hydration energy with the strength of intermolecular forces between water molecules which doesn't make sense for the same reason as for option (A).

Analyzing each option in relevance with the nature of the exothermic dissolution of calcium chloride, the most reasonable option that accurately describes the enthalpy of the solution is Option (B) because the energy released during hydration is greater than the energy used up to break the lattice of the solid.