A certain reaction has DH^$\circ$_rxn = +177.8 kJ, and DS^$\circ$_rxn = +160.5 J/K. Above what temperature does it become product-favored ?

Question

Quizplus · Accepted Answer

The condition for a reaction to become product-favored is ΔG < 0, and we know that

ΔG = ΔH - TΔS

We can convert the units of ΔS to kJ/K by dividing by 1000:

ΔS = 160.5 J/K = 0.1605 kJ/K

Plugging in the values we have:

ΔG = +177.8 kJ - T(0.1605 kJ/K)

Solving for T:

ΔG < 0
- T(0.1605 kJ/K) < -177.8 kJ
T > 1108°C or 1381 K

The answer choices are in Celsius, so the correct choice is C, 835°C.

A Certain Reaction Has DH ∘\circ∘ rxn = +177 ∘\circ∘ rxn = +160