For the reaction, X→Y ,   ΔH = −36kJ/mole ;   ΔS = −90Jk−1mole−1 the reaction is spontaneous ( ΔH & ΔS do not vary with temperature) at

ΔG = ΔH−TΔSAt equilibrium, ∆G=0∴ Teq = ΔHΔSTeq = −36×103Jmole−1−90JK−1mole−1Teq = 400KΔG = ΔH−TΔSΔG = −ve−T−ve∆G  will be negative only when T is less than Teq