Which of the following steps in the formation of a solution is exothermic?

• A. The vaporization of the solvent
• B. The separation of solvent particles
• C. The interaction between solute and solvent particles
• D. The separation of solute particles

Answer: (C)

Verified step by step guidance

1. Understand that the formation of a solution involves three main steps: (1) separation of solute particles, (2) separation of solvent particles, and (3) interaction between solute and solvent particles.
2. Recognize that separating solute particles requires energy to overcome intermolecular forces holding them together, so this step is endothermic (absorbs energy).
3. Similarly, separating solvent particles also requires energy to break intermolecular forces between solvent molecules, making this step endothermic as well.
4. The interaction between solute and solvent particles releases energy because new intermolecular attractions form, which makes this step exothermic (releases energy).
5. Therefore, the exothermic step in solution formation is the interaction between solute and solvent particles, as it compensates for the energy absorbed in the separation steps.