Which of the following is completely true about the relationship between ΔG and T for this reaction?

Question

For the reaction, Fe₂O₃ (s) + 3 H₂(g) <=> 2 Fe(s) + 3 H₂O(g), ΔG° = 53 kJ at 25 °C and ΔH° = 100 kJ. Which of the following is completely true about the relationship between ΔG and T for this reaction?

The correct answer is  ΔG < 0 when T > 635 K

can you explain why

Answer 1

Must use Gibbs equation to calculate entropy.

ΔG = ΔH - TΔS

53KJ = 100KJ - 298 K ΔSΔ

Δ S = .158 KJ/K

Use the enttopy to calculate the temperature in which ΔG = 0 , this is the temperature where the reaction changes of being spontaneous to non nonspontaneous.

0 KJ = 100KJ - T ( .158 KJ/ K)

T = 634 K

Therefore any temperature greater greater than 634 K, ΔG will always be negative.