Consider the following reaction and its deltaH^0_don and deltaG^0 _don values at

Question

Consider the following reaction and its deltaH^0_don and deltaG^0 _don values at 25 degree C. Evaluate deltas^0_Don at 25 degree C. 2C_2H_2(g)+5O_2(g) 4CO_2(g)+2H_2O(i) deltaH^0_Don = 2599 kj, deltaG^0_Don = 2470 kj +340 j/k -340 j/k +386 j/k -433 j/k -386 j/k Which of the following statement regarding the third law of thermodynamics is incorrect? The absolute S is zero at 0 kelvin. The absolute S at 298 K can be positive or negative. Pure substances have positive absolute S at T>0 Kelvin. Absolute zero gives a reference point for determining absolute S. The absolute S is greater at 300 K than 100 K for a given substance.

Explanation / Answer

        Given that T = 25oC = 25 + 273 K = 298 K

                         Gorxn = - 2470 kJ = - 2470 x 103 J

                        Horxn = - 2599 kJ = - 2599 x 103 J

   We know that Gorxn = Horxn - TSorxn

     Then,

      TSorxn = Horxn - Gorxn

       Sorxn = [Horxn - Gorxn]/T

                  = [( -2599 x 103 J) - (-2470 x 103 J)] / 298 K

                  = - 433 J/K

Therefore,

Sorxn = - 433 J/K

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