Unit 5 of 5
Study guide for CLEP CLEP Chemistry — Unit 5: Thermodynamics and Kinetics. Practice questions, key concepts, and exam tips.
60
Practice Questions
18
Flashcards
4
Key Topics
Try these 5 questions from this unit. Sign up for full access to all 60.
What is the standard reduction potential of the half-reaction Cu2+ + 2e- → Cu?
Answer: C — +0.34 V is correct because the standard reduction potential of the half-reaction Cu2+ + 2e- → Cu is +0.34 V. The most tempting distractor, -0.34 V, would be the oxidation potential.
What is the effect of increasing temperature on the value of Kc for an exothermic reaction?
Answer: E — Increasing temperature decreases the value of Kc for an exothermic reaction, as the equilibrium shifts to the left to consume heat and re-establish equilibrium. This occurs because exothermic reactions release heat, so higher temperatures favor the reverse reaction, reducing Kc.
Consider a system where ΔH = 50 kJ and TΔS = 70 kJ at 300 K. What is the sign of ΔG?
Answer: D — Negative is correct because ΔG = ΔH - TΔS = 50 kJ - 70 kJ = -20 kJ, which is negative. A positive ΔG is incorrect as it would indicate non-spontaneity.
What is the main assumption of Hess's law?
Answer: C — Enthalpy is a state function is correct because Hess's law relies on the fact that enthalpy is a state function, meaning its value depends only on the initial and final states of the system, not on the path taken.
What is the sign of ΔG for a spontaneous reaction?
Answer: D — Negative is correct because negative ΔG indicates spontaneity..
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