Under what conditions will a reaction be spontaneous if
(i) both `DeltaH` and `DeltaS` are positive?
(ii) both `DeltaH` and `DeltaS` are negative?

Explanation

`DeltaG = DeltaH - TDeltaS` and for a reaction to be spontaneous `DeltaG` should be `-ve`.
(i) Both `DeltaH` and `DeltaS` are positive so that `DeltaG` will be negative only if `TDeltaS gt DeltaH` in magnitude.
`DeltaG = DeltaH - TDeltaS`
`= (+) -T(+)`
Thus either `DeltaS` shuld be very large so that even if T is low, `TDeltaS` is greater than `DeltaH`, or if `DeltaS` is small, T should be high so that `TDeltaS gt DeltaH`
If both `DeltaH` and `DeltaS` are negative, `DeltaG` can be negative only if `TDeltaS lt DeltaH` in magnitudde.
`DeltaG = DeltaH -TDeltaS`
` = (-) -T(-)`
This is possible only if either `DeltaH` has large negative value or T is so low that `TDeltaS lt DeltaH`.