Question

A chemical reaction is spontancous at `298 K` but non spontaneous at `350 K` . Which one of the following is true for the reaction ?
A. `{:(,DeltaG,DeltaH,DeltaS),(A,-,-,+):}`
B. `{:(,DeltaG,DeltaH,DeltaS),(B,+,+,+):}`
C. `{:(,DeltaG,DeltaH,DeltaS),(C,-,+,-):}`
D. `{:(,DeltaG,DeltaH,DeltaS),(D,+,-,+):}`

Answer 1

Correct Answer - C
In case of `(D)`
`DeltaG=(DeltaH)/(-ve)-(TDeltaS)/(+ve)`
At low temperature, `-TDeltaS` will be `+ve` and less `-DeltaH`.
`:. DeltaG` will be negative and the reaction will be spontaneous
At high temperature, `-TDeltaS` will be `+ve` and greater than `-DeltaH`
`:. DeltaG` becomes `+ve` and the reaction will be non-spontaneous.