Which statement best describes the change that is associated with the enthalpy of solution?
each step of the process is exothermic when the enthalpy of solution is negative.
each step of the process is endothermic when the enthalpy of solution is positive.
two steps of the process are exothermic, and one step is endothermic.
two steps of the process are endothermic, and one step is exothermic.

The correct option is D. Enthalpy of solution is defined as the heat change associated with the dissolution of a substance in a solvent at constant pressure leading to infinite dilution. Dissolution usually occur in three steps:
1. breaking of the inter- molecular forces which holds the molecules of the substance to be dissolved together. This reaction is endothermic.
2. the breaking of the inter molecular forces which the particles of the solvent together. This reaction is also endothermic.
3. the formation of attraction between the solute and the solvent. This reaction is exothermic.
Thus, out of the three steps of the reaction, two are endothermic while one is exothermic.