Consider a reaction where S rxn = -315 J/K and H rxn = -45.6 kJ. Which statement

Question

Consider a reaction where S rxn = -315 J/K and H rxn = -45.6 kJ. Which statement is true about the spontaneity of this reaction?

Consider a reaction where S rxn = -315 J/K and H rxn = -45.6 kJ. Which statement is true about the spontaneity of this reaction?

This reaction is spontaneous at 25°C, but will become nonspontaneous if the temperature is decreased to -130°C. This reaction is nonspontaneous at 25°C but will become spontaneous if the temperature is increased to 145°C. Decreasing the temperature will have no effect on the spontaneity of the reaction. It is nonspontaneous at 25°C and will become even less spontaneous as the temperature decreases. This reaction is nonspontaneous at 25°C but will become spontaneous if the temperature is decreased to -130°C.

Explanation / Answer

delta G = delta H - T delta S

when G= -ve , reaction will be spontaneous.

when G= +ve , reaction will be nonspontaneous.

Since both H and S = - ve, to be spontaneous TS has to be very small.

That is when T is very low then only reaction is spontaneous.

ans - This reaction is nonspontaneous at 25°C but will become spontaneous if the temperature is decreased to -130°C.

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