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An endotthermic reaction is non-spontane...

An endotthermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then:

A

`DeltaH` is `-ve, DeltaS` is `+ve`

B

`DeltaH` and `DeltaS` both are `+ve`

C

`DeltaH` and `DeltaS` both are `-ve`

D

`DeltaH` is `+ve`, `DeltaS` is -ve

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The correct Answer is:
To solve the problem, we need to analyze the conditions under which an endothermic reaction can become spontaneous. Let's break down the steps: ### Step 1: Understand the spontaneity of reactions For a reaction to be spontaneous, the change in Gibbs free energy (ΔG) must be negative. The relationship between ΔG, enthalpy change (ΔH), and entropy change (ΔS) is given by the equation: \[ \Delta G = \Delta H - T \Delta S \] ### Step 2: Analyze the given conditions The problem states that the reaction is endothermic, which means: - ΔH > 0 (positive enthalpy change) At the freezing point of water (0°C or 273 K), the reaction is non-spontaneous, which implies: \[ \Delta G > 0 \] At the boiling point of water (100°C or 373 K), the reaction becomes feasible (spontaneous), which implies: \[ \Delta G < 0 \] ### Step 3: Apply the Gibbs free energy equation At the freezing point (T = 273 K): \[ \Delta G = \Delta H - (273 \, \text{K}) \Delta S > 0 \] This can be rearranged to: \[ \Delta H < (273 \, \text{K}) \Delta S \] At the boiling point (T = 373 K): \[ \Delta G = \Delta H - (373 \, \text{K}) \Delta S < 0 \] This can be rearranged to: \[ \Delta H < (373 \, \text{K}) \Delta S \] ### Step 4: Compare the two inequalities From the two inequalities, we have: 1. At freezing point: \( \Delta H < (273 \, \text{K}) \Delta S \) 2. At boiling point: \( \Delta H < (373 \, \text{K}) \Delta S \) Since the reaction is endothermic (ΔH > 0), for the reaction to become spontaneous at higher temperatures, ΔS must be positive. This means that the entropy of the system increases during the reaction. ### Conclusion Thus, we conclude that for the endothermic reaction to be non-spontaneous at the freezing point and spontaneous at the boiling point, we must have: - ΔH > 0 (endothermic) - ΔS > 0 (positive entropy change) ### Final Answer The correct option is that both ΔH is positive and ΔS is positive. ---

To solve the problem, we need to analyze the conditions under which an endothermic reaction can become spontaneous. Let's break down the steps: ### Step 1: Understand the spontaneity of reactions For a reaction to be spontaneous, the change in Gibbs free energy (ΔG) must be negative. The relationship between ΔG, enthalpy change (ΔH), and entropy change (ΔS) is given by the equation: \[ \Delta G = \Delta H - T \Delta S \] ### Step 2: Analyze the given conditions The problem states that the reaction is endothermic, which means: ...
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Free enegry , G = H - TS , is state function that indicates whther a reaction is spontaneous or non-spontaneous. If you think of TS as the part of the system's enegry that is disordered already, then (H -TS) is the part of the system's energy that is still ordered and therefore free to cause spontaneous change by becoming disordered. Also, DeltaG = DeltaH - T DeltaS From the second law of thermodynamics, a reaction is spontaneous if Delta_("total")S is positive, non-spontaneous if Delta_("total")S is negative, and at equilibrium if Delta_('total")S is zero. Since, -T DeltaS = DeltaG and since DeltaG and DeltaS have opposite sings, we can restate the thermodynamic criterion for the spontaneity of a reaction carried out a constant temperature and pressure. IF DeltaG lt 0 , the reaction is spontaneous. If DeltaG gt 0 , the reaction is non-spontaneous. If DeltaG = 0 , the reaction is at equilibrium. Read the above paragraph carefully and answer the following questions based on the above comprehension. If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then

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