# Is it true if so the reaction diamond graphite should

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Is it true? If so, the reaction diamond graphite should not be thermodynamically allowed. I Δ r G = Δ f G (graphite) - Δ f G (diamond) = - 2 . 9 kJ / mol < 0 I From this calculation, we conclude that the conversion of diamond to graphite is thermodynamically allowed. I It would seem that the diamond industry’s claim that diamonds are forever is faulty.

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Example: Conversion of graphite to diamond I At ambient temperature and pressure, diamond is metastable , which is to say that it is not in true thermodynamic equilibrium with its surroundings, but that it is trapped, at least temporarily, in a non-equilibrium state. I The structural rearrangement required to make graphite from diamond is so unlikely as to be essentially impossible at room temperature, so for most practical purposes, diamonds are, if not forever, then exceedingly long lived. I Thermodynamics tells us what can happen, not what will happen. I However, if we provide a little heat. . .
Activity: Measuring the deviation from standard conditions I It is rare that we run a reaction under standard conditions. I The activity ( a ) of a substance measures its deviation from the standard state. I a = 1 for a substance in the standard state. I The activity is a dimensionless quantity.

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Activities of ideal substances Ideal gas: Defined by negligible intermolecular forces, always true at sufficiently low pressures a = p / p , p = 1 bar Solid: a = 1 Ideal solvent: Intermolecular forces experienced by solvent essentially identical to those in the pure solvent, true if the solvent and solute are chemically similar or if the solute is at a sufficiently low concentration a = X (mole fraction = n solvent / n i ) (But usually, X 1 for the solvent.) Ideal solute: Negligible intermolecular forces between solute molecules, always true at sufficiently low concentrations a = c / c , c = 1 mol / L

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