Question

For the reaction H2(g) + S(s) --> H2S(g)

delta H = -20.2 kJ mol-1 and delta S =+43.1 J K-1mol-1. Which of the following statements is true?

The reaction is spontaneous at all temperatures.

delta G becomes less favorable as T is raised.

The reaction is only spontaneous at high temps.

The reaction is only spontaneous at low temps.

The reaction is at equilibrium at 25 C under standardconditions.

Please explain why too. Thank you, feedback will beawarded as soon as I receive the correct answer.

Answer 1

ΔG = ΔH - TΔS

ΔG must be negative for the rxn to be spontaneous.
When ΔH and ΔS have different signs, you know that whatever pattern there is must be true at all temps.
When ΔH and ΔS have the same sign, you know that thepattern is temperature dependent.

Here, ΔH and ΔS have different signs, so you know thepattern that ΔG has must be true of all temperatures. Usestandard temp 298K to determine the pattern.
ΔG = -20.2 kJ - (298)(.0431 J)
ΔG = -33 kJ
The rxn is spontaneous at all temperatures.