question_answer

A reaction occurs spontaneously if:                                                                                 [AIPMT (S) 2005]

A)   \[T\Delta S<\Delta H\] and both \[\Delta H\] and \[\Delta S\] are +ve

B)  \[T\Delta S>\Delta H\] and both \[\Delta H\] and \[\Delta S\] are +ve

C)        \[T\Delta S=\Delta H\] and both \[\Delta H\] and \[\Delta S\] are +ve

D)       \[T\Delta S>\Delta H\] and  \[\Delta H\] is + ve and \[\Delta S\] is -ve

Correct Answer: B

Solution :

The spontaneity of reaction is based upon the negative value of  is based upon  and    according to following equation (Gibbs-Helmholtz equation)

If the magnitude of  is negative, then the reaction is spontaneous, when  and  and    are +ve, then  is negative.