The dissolution of gases in water is virtually always exothermic because _.
A) neither of the two endothermic steps in the solution- formation process is necessary
B) one of the two endothermic steps (separation of solute particles) in the solution- formation process is unnecessary
C) gases react exothermically with water
D) the exothermic step in the solution- formation process is unnecessary
E) all three steps in the solution- formation process are exothermic

Question

Quizplus · Accepted Answer

The solution-formation process for dissolution of gases in water involves two endothermic steps: the separation of solute particles and the breaking of hydrogen bonds in water molecules. The dissolution of gases in water is exothermic because the energy released by the formation of new solute-solvent interactions (which is exothermic) is greater than the energy required during the breaking of hydrogen bonds in water molecules (which is endothermic). However, the separation of solute particles (which is also endothermic) is not necessary for gas dissolution in water, thus making option B the correct choice.

The Dissolution of Gases in Water Is Virtually Always Exothermic