Question

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?

Answer 1

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

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

Step-by-step 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.