Question

5. For a given reaction Delta H Standard = -45 kJ and Delta S Standard = -103 J/K.

A. Is the reaction spontaneous? At what T does it become spontaneous?

B. What is Delta G at 450 K?

Answer 1

5)

A)

deltaH = -45.0KJ

deltaS = -103J/K

= -0.103 KJ/K

we have below equation to be used:

deltaG = deltaH - T*deltaS

for reaction to be spontaneous, deltaG should be negative

that is deltaG<0

since deltaG = deltaH - T*deltaS

so, deltaH - T*deltaS < 0

-45.0- T *-0.103 < 0

T *0.103 < 45.0

T < 437 K

So, the reaction will be spontaneous at standard temperature as well which is 273 L

Answer: yes

B)

deltaH = -45.0KJ

deltaS = -103J/K

= -0.103 KJ/K

T = 450 K

we have below equation to be used:

deltaG = deltaH - T*deltaS

deltaG = -45.0 - 450.0 * -0.103

deltaG = 1.35 KJ

Answer: 1.35 KJ