CHEM 1E03 Lecture 22: Entropy and Gibbs Free Energy

Elemental carbon usually exists in one of two forms: graphite or diamond. It is generally believed that diamonds last forever. The table shows the standard enthalpy of formation ( Constants | Periodic Table Gibbs free energy is a measure of the spontaneity of a chemical reaction. It is the chemical potential for a reaction, and is minimized at equilibrium. The change in Gibbs free energy can be calculated by Hi, ) and the standard molar entropy (S*) values for diamond and graphite Substance AH (kJ/mol) S° (J/mol-K) 5.740 graphite Cdiamond 1.897 2.38 where ΔGrn is the standard Gibbs free energy change for a reaction, Δ n is the standard enthalpy change for a reaction, T is the temperature in kelvins, and Δ&n is the standard entropy change for a reaction. Part A For a reaction at equilibrium, ΔGrxn is equal to zero. For negative values, the reaction is spontaneous, and for positive values the reaction is nonspontaneous What is the standard Gibbs free energy for the transformation of diamond to graphite at 298 K? Cdiamond →Cgraphite Express your answer to three significant figures and include the appropriate units View Available Hint(s) 2.90 kJ mol SubmitPrev evious Answer Incorrect, Try Again: 6 attempts remaining