If a reaction has a positive enthalpy change (ΔH > 0) and a negative entropy change (ΔS < 0), what can be concluded about its spontaneity?
Answer and explanation
Correct answer: C. It is non-spontaneous at all temperatures
- Step 1: Examine the Gibbs equation: .
- Step 2: When (positive) and (negative), is positive at all positive absolute temperatures . Thus always, making the reaction non-spontaneous at all temperatures.
Answer
It is non-spontaneous at all temperatures.
Why not the others: Spontaneous at all temperatures requires and ; high/low temperature dependencies occur when both signs are positive or both negative.
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