For the reaction 2A+B`rarr`C at 298 K, `DeltaH=400kJ mol^-1` and `DeltaS=0.2 kJk^-1mol^_1`. At what temperature will be reaction become spontaneous considering `DeltaH` and `DeltaS` to be constant over the temperature range.

Explanation

At equilibrium, `DeltaG`=0`therefore` DeltaH-TDeltaS`=0 or `DeltaH=TDeltaS` `therefore` T=`DeltaH/DeltaS=400/0.2=2000K`
i.e the reaction will be at equilibrium at 2000K. Since `DeltaH`and `DeltaS` are positive`DeltaG` will be negative when `Tdeltas>DeltaH`. This takes place at higher temperature. Therefore, the reaction will be sopntaneous at temperature above 2000K.