(D) For a reaction to be spontaneous,the Gibbs free energy change $ \Delta G = \Delta H - T \Delta S $ must be negative $( \Delta G < 0 )$.If $ \Delta

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$ \Delta H $ is $ +ve $; $ \Delta S $ is $ -ve $

(D) For a reaction to be spontaneous,the Gibbs free energy change $ \Delta G = \Delta H - T \Delta S $ must be negative $( \Delta G If $ \Delta H $ is $ +ve $ (endothermic) and $ \Delta S $ is $ -ve $ (decrease in entropy),then $ \Delta G = (+ve) - T(-ve) = (+ve) + (T \times +ve) = +ve $.Since $ \Delta G $ is always positive regardless of the temperature $ T $,the reaction is impossible under any conditions.

Class 11 Chemistry Thermodynamics Free energy and Work

Medium

The occurrence of a reaction is impossible if

AIIMS 1982 All AIIMS

AIIMS 1991 All AIIMS

A
$ \Delta H $ is $ +ve $; $ \Delta S $ is also $ +ve $ but $ \Delta H < T \Delta S $
B
$ \Delta H $ is $ -ve $; $ \Delta S $ is also $ -ve $ but $ \Delta H > T \Delta S $
C
$ \Delta H $ is $ -ve $; $ \Delta S $ is $ +ve $
D
$ \Delta H $ is $ +ve $; $ \Delta S $ is $ -ve $