MCAT General Chemistry Question 202: Answer and Explanation

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Question: 202

6. The shape of the carbonate ion is:

  • A. The rate constant for the unfavorable reactions is very large.
  • B. The cycle contains exergonic reactions that drive the endergonic reactions forward.
  • C. The endothermically unfavorable reactions also have a negative entropy change.
  • D. The activation energies of the unfavorable reactions are lowered by catalysts.

Correct Answer: B

Explanation:

B The question is asking about thermodynamic principles, so answer choices A and D that involve kinetics can be eliminated. Reactions with a positive ∆H and a negative ∆S are never spontaneous according to ∆G = ∆H – T∆S, eliminating choice C. If the sum of all reactions is more exergonic (–∆G) than endergonic (+∆G), the net release of free energy will drive the cycle forward, making choice B the best answer.

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