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A reaction occurs spontaneously if :

  1. A
    T∆S < ∆H and both ∆H and ∆S are +ve
  2. B
    T∆S > ∆H and both ∆H and ∆S are +ve
  3. C
    T∆S = ∆H and both ∆H and ∆S are +ve
  4. D
    T∆S > ∆H and ∆H is + ve and ∆S is -ve

Solution & Step-by-step Explanation

A reaction is spontaneous if the Gibbs free energy change (∆G) is negative. The equation for ∆G is ∆G = ∆H - T∆S, where ∆H is the enthalpy change, T is the temperature in Kelvin, and ∆S is the entropy change. For a reaction to be spontaneous, ∆G must be negative. This can occur under two conditions: (1) if ∆H is negative (exothermic reaction) and ∆S is positive (increase in disorder), or (2) if T∆S > ∆H, meaning the entropy term dominates, even if ∆H is positive (endothermic reaction), as long as ∆S is positive and the temperature is high enough. Therefore, the correct condition for a spontaneous reaction is when T∆S > ∆H and both ∆H and ∆S are positive.

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A reaction occurs spontaneously if :
A
T∆S < ∆H and both ∆H and ∆S are +ve
B
T∆S > ∆H and both ∆H and ∆S are +ve
C
T∆S = ∆H and both ∆H and ∆S are +ve
D
T∆S > ∆H and ∆H is + ve and ∆S is -ve

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