For the reaction at `298 K`
`2A+B rarr C`
`DeltaH=400 kJ mol^(-1)` and `DeltaS=0.2 kJ K^(-1) mol^(-1)`
At what temperature will the reaction becomes spontaneous considering `DeltaH` and `DeltaS` to be contant over the temperature range.

Explanation

T=298 K
`DeltaH=400 "Jmol^(-1) =400 "J mol^(-1)`
`DeltaS=0.2J K - 1 " mol"^(-1)`
`DeltaG=DeltaH-TDeltaS`
if ` T = 2000K`
`DeltaG = 400-(0.2xx2000)=0`
if `T gt 2000K`
`DeltaG` will be negative.
The reaction would be spontaneous only beyond 2000K.