Question

For a particular reaction, ΔH° is -28.4 kJ and ΔS is -87.9 J/K. Assuming these values change very little with temperature, over what temperature range is the reaction spontaneous in the forward direction?

Answer 1

deltaHo = -28.4 KJ

deltaSo = -87.9 J/K

= -0.0879 KJ/K

we have below equation to be used:

deltaGo = deltaHo - T*deltaSo

for reaction to be spontaneous, deltaGo should be negative

that is deltaGo<0

since deltaGo = deltaHo - T*deltaSo

so, deltaHo - T*deltaSo < 0

-28.4- T *-0.0879 < 0

T *0.0879 < 28.4

T < 323 K

Answer: reaction is spontaneous for temperature less than 323 K

Feel free to comment below if you have any doubts or if this answer do not work. I will edit it if you let me know