Concept:Dissolving an ionic compound involves two main energy changes: breaking the crystal lattice and hydrating the separated ions.
Explanation:The heat of solution is the overall heat change when one mole of a solute dissolves in a solvent.
It is the sum of two energy terms:
Lattice energy is the energy needed to separate the ionic solid into gaseous ions.
This process is endothermic, so lattice energy has a positive value.
Hydration energy is the energy released when gaseous ions are surrounded by water molecules.
This process is exothermic, so hydration energy has a negative value.
Combining these gives the equation:
Heat of solution=Lattice energy+Hydration energyTherefore, the two energies involved in the heat of solution are lattice energy and hydration energy.
Answer:A. lattice energy and hydration energy.