Problem: What is the standard Gibbs free energy for the transformation of diamond to graphite at 298 K?Elemental carbon usually exists in one of two forms: graphite or diamond. It is generally believed that diamonds last forever. Here are the standard enthalpy of formation (ΔH°f) and the standard molar entropy (S°) values for diamond and graphite.SubstanceH°f (kJ/mol)S° (J/mol•K)Cgraphite05.740Cdiamond1.8972.38

FREE Expert Solution

We’re being asked to determine the ΔG˚rxn at 298 K for the reaction:

Cdiamond → Cgraphite



We’re given the ΔH˚f and S˚ of each reactant and product.

SubstanceH°f (kJ/mol)S° (J/mol•K)
Cgraphite05.740
Cdiamond
1.8972.38


We can use the following equation to solve for ΔG˚rxn:


ΔG°rxn=ΔH°rxn-TΔS°rxn


For this problem, we need to do the following steps:

Step 1: Calculate ΔH˚rxn.

Step 2: Calculate ΔS˚rxn.

Step 3: Use ΔH˚rxn and ΔS˚rxn to calculate for ΔG˚rxn.



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Problem Details

What is the standard Gibbs free energy for the transformation of diamond to graphite at 298 K?

Elemental carbon usually exists in one of two forms: graphite or diamond. It is generally believed that diamonds last forever. Here are the standard enthalpy of formation (Δf) and the standard molar entropy () values for diamond and graphite.

SubstanceH°f (kJ/mol)S° (J/mol•K)
Cgraphite05.740
Cdiamond1.8972.38


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