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Enthalpy of Reaction
[2ΔHf(Hg (ℓ)) + 1ΔHf(O2 (g))] - [2ΔHf(HgO (s red orthorhombic))]
[2(0) + 1(0)] - [2(-90.83)] = 181.66 kJ
181.66 kJ (endothermic)
[2ΔSf(Hg (ℓ)) + 1ΔSf(O2 (g))] - [2ΔSf(HgO (s red orthorhombic))]
[2(76.02) + 1(205.03)] - [2(70.29)] = 216.49 J/K
216.49 J/K (increase in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(Hg (ℓ)) + 1ΔGf(O2 (g))] - [2ΔGf(HgO (s red orthorhombic))]
[2(0) + 1(0)] - [2(-58.56)] = 117.12 kJ
117.12 kJ (nonspontaneous)
From ΔG = ΔH - TΔS:
117.11 kJ (nonspontaneous)
Equilibrium Constant, K (at 298.15 K)
This process is not favorable at 25°C.
Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 74.