University Science Books General Chel stry cQuarrie Peter A. Rock Ethan Gallogly

Question

University Science Books General Chel stry cQuarrie Peter A. Rock Ethan Gallogly presented by Sapling Learn Donald M Calculate the standard entropy, AS of the following reaction at 25.0 C using the data in this table The standard enthalpy of the reaction, AHorxn, is -633.1 kJ. mol Number AS J. K mol Then, calculate the standard Gibbs free energy of the reaction, AGnn. Number J. mol kJ AG Finally, determine which direction the reaction is spontaneous as written at 25.0 Cand standard pressure forward reverse O both neither

Explanation / Answer

Delta S of reaction = Delta S of product - Delta S of reactant

= Delta S of C6H6 - 3X Delta S C2H2   ( these are standard values)

= 154.9 - 3X200.9 = -447.8 J / K mole = -0.447 KJ / K mole

now Delta G = Delta H - T DeltaS

Delta H = -633.1 KJ / mole

T = 298 K (273+ 25 K)

Delta G = -633.1 - 298 X(- 0.447 )= -633.1 +133.21 = -499.89 KJ / moles

The negative value of free energy change shows that reaction will be spontaneous in forward direction.

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