MCAT General Chemistry Question 125: Answer and Explanation
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Question: 125
5. The process of formation of a liquid solution can be better understood by breaking the process into three steps:
1. Breaking the solute into its individual components
2. Making room for the solute in the solvent by overcoming intermolecular forces in the solvent
3. Allowing solute–solvent interactions to occur to form the solution
Which of the following correctly lists the enthalpy changes for these three steps, respectively?
- A. Endothermic, exothermic, endothermic
- B. Exothermic, endothermic, endothermic
- C. Exothermic, exothermic, endothermic
- D. Endothermic, endothermic, exothermic
Correct Answer: D
Explanation:
The first step will most likely be endothermic because energy is required to break molecules apart. The second step is also endothermic because the intermolecular forces in the solvent must be overcome to allow incorporation of solute particles. The third step will most likely be exothermic because polar water molecules will interact with the dissolved ions, creating a stable solution and releasing energy.