The occurrence of a reaction is impossible if

Options

A. `Delta H` is +ve , `Delta S` is also + ve but `Delta H lt T Delta S`
B. `Delta H` is-ve, `Delta S` is also - ve but `Delta H gt T Delta S`
C. `Delta H` is - ve, `Delta S` is + ve
D. `Delta H` is + ve, `Delta S` is - ve

Answer

D

Explanation

`Delta G= Delta H- T Delta S= 0`
`therefore T= (Delta H)/(Delta S)= (+30.558kJ mol^(-1))/(0.066 kJ K^(-1) mol^(-1))= 463K`
`Delta G = Delta H- T Delta S= (30.558 - T xx 0.066) kJ mol^(-1)` at `T lt 463K`
`0.066T lt 463 xx 0.066`
or `0.066T lt 30.558`
or `0 lt 30.558 - 0.066T`
or `0 lt Delta G`
Thus, at `T lt 463K, Delta G gt 0`
i.e., process is non spontaneous.