For a reaction , delta H = -40kJ and delta S = -50 J/K. At what temperature range ll it change from spontaneous to non spontaneous ?

Question

a) 0.8 K to 1K

b) 799 K to 800 K

c) 800 K to 801 K

d) 799 K to 801 K

Answer 1

For a reaction to be spontaneous, delta G should be negative. Looking at the equation

ΔG = ΔH - TΔS

Substitute -40 kJ for ΔH and -0.05 kJ /K for ΔS and find what values of T result in a negative ΔG 

NOTE: Change units of ΔS to be same for ΔH