A reaction has ΔH < 0 and ΔS < 0. At what temperature will the forward reaction proceed?
Understand the Problem
The question is asking under what conditions (specifically temperature) a chemical reaction will proceed given that it has a negative enthalpy change (ΔH < 0) and a negative entropy change (ΔS < 0). This relates to thermodynamic principles regarding Gibbs free energy and reaction spontaneity.
Answer
Low temperatures.
The forward reaction will proceed at low temperatures when both ΔH < 0 and ΔS < 0.
Answer for screen readers
The forward reaction will proceed at low temperatures when both ΔH < 0 and ΔS < 0.
More Information
When ΔH < 0 and ΔS < 0, the reaction is exothermic and decreases in entropy. Lowering the temperature ensures the enthalpy term dominates, allowing ΔG to be negative and the reaction to proceed.
Tips
Common mistake is to assume reactions with negative ΔS cannot be spontaneous, but at low temperatures, the exothermic nature (ΔH < 0) can drive spontaneity.
Sources
- A certain process has Delta H < 0, Delta S < 0. This process is ... - homework.study.com
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