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The change in entropy, Delta S is positi...

The change in entropy, `Delta S` is positive for an endothermic reaction, if enthalpy change `Delta H` occurs at the same temperature T, then the reaction is feasible

A

at all temperatures

B

when `DeltaH gt TDeltaS`

C

when `DeltaH lt TDeltaS`

D

not feasible at all

Text Solution

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The correct Answer is:
To determine the feasibility of an endothermic reaction with a positive change in entropy, we can analyze the relationship between Gibbs free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS). **Step-by-Step Solution:** 1. **Understand the Gibbs Free Energy Equation:** The Gibbs free energy change is given by the equation: \[ \Delta G = \Delta H - T \Delta S \] where: - ΔG = change in Gibbs free energy - ΔH = change in enthalpy - T = temperature in Kelvin - ΔS = change in entropy 2. **Identify Conditions for Feasibility:** For a reaction to be feasible (spontaneous), the change in Gibbs free energy must be negative: \[ \Delta G < 0 \] 3. **Substitute the Gibbs Free Energy Equation:** From the requirement for feasibility, we can rewrite the equation: \[ \Delta H - T \Delta S < 0 \] Rearranging gives: \[ \Delta H < T \Delta S \] 4. **Analyze the Given Conditions:** The problem states that the reaction is endothermic, which means: - ΔH > 0 (enthalpy change is positive) - ΔS > 0 (entropy change is positive) 5. **Conclusion on Feasibility:** Since both ΔH and ΔS are positive, for the reaction to be feasible, the condition ΔH < TΔS must hold true. This means that the increase in entropy must be sufficiently large to overcome the positive enthalpy change. 6. **Final Statement:** Therefore, if ΔH is less than TΔS, the reaction is feasible. **Correct Option:** The correct option is **C: ΔH < TΔS**. ---
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