Elemental carbon usually exists in one of two forms: graphite or diamond. It is
ID: 953606 • Letter: E
Question
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 (Hf) and the standard molar entropy (S) values for diamond and graphite.
What is the standard Gibbs free energy for the transformation of diamond to graphite at 298 K?
CdiamondCgraphite
Express your answer to three significant figures and include the appropriate units.
Substance Hf (kJ/mol) S (J/molK) Cgraphite 0 5.740 Cdiamond 1.897 2.38Explanation / Answer
Ggraphite = H - TF = 0 - 298*5.74 = -1710.52 J
Gdiamond = H-TF = 1897 - 298*2.38 = 1187.76 J
then
dG = Ggraphite - Gdiamond = -1710.52 -1187.76 = -2898.28 J
dG = -2.90 kJ/mol
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