Question

The standard molar entropy of benzene is 173.3 J/K-mol. Calculate the change in its standard molar Gibbs energy when benzene is heated from 25C to 45C.

Answer 1

Solution :-

Standard molar enthalpy of the benzene = 49000 J/mol

Standard lets calculate the free energy at the 25 C = 298 K

and 45 C = 318 K

Delta G = Delta H - T*delta S

             = 49000 J - (298*173.3 J per mol K)

             = -2643.4 J /mol

Delta G = 49000 J per mol - (173.3 J per mol K * 318 K)

              = -6109.4 J per mol

so the change in the free energy is = -61.09.4 J - (-2643.4 J) = -3466 J

-3466 J * 1 kJ / 1000 J = -3.466 kJ