MCAT General Chemistry Question 280: Answer and Explanation
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Question: 280
6. What is true regarding the enthalpy and entropy changes for Step 3 of the mechanism?
- A. ∆H > 0, ∆S > 0
- B. ∆H > 0, ∆S < 0
- C. ∆H < 0, ∆S > 0
- D. ∆H < 0, ∆S < 0
Correct Answer: D
Explanation:
D Neutralization reactions release large amounts of heat, so ∆H must be less than zero, eliminating choices A and B. From the point of view of entropy, two molecules become one, increasing the order of the system. Moreover, two aqueous species turning into a pure liquid increases order. Therefore, disorder decreases and ∆S must be less than zero.