the reaction Br2 (l) - >Br2 (g) has a deltaH=30.91 kJ and a deltaS=.0933 kJ/K. at what temperature does this reaction become spontaneous? Below this temperature, is the forward reaction or the backward reaction favored?

The temperature above which the reaction be spontaneous is 331.3 K.

Below this temperature; the backward reaction is the favored reaction.

Explanation:

We have an important relation from the third law of thermodynamics:

ΔG = ΔH - TΔS

ΔG is the free energy change of the reaction,

ΔH is the enthalpy change of the reaction,

ΔS is the entorpy change of the reaction,

The reaction is spontaneous when ΔG is negative. and ΔG be negative when the value of (TΔS) is higher than the value of (ΔH).

When ΔG = 0, ΔH = TΔS.

For this reaction, ΔH = 30.91 KJ and ΔS = 0.0933 KJ/K.

The temperature above which the reaction be spontaneous is:

T = ΔH / ΔS = (30.91 KJ) / (0.0933 KJ/K) = 331.29 K ≅ 331.3 K.

∴ The temperature above which the reaction be spontaneous is 331.3 K.

Below this temperature; the backward reaction is the favored reaction.