Estimating a phase transition temperature from standard thermodynamic data

Estimating a phase transition temperature from standard thermodynamic data

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Estimating a phase transition temperature from standard thermodynamic data Write the phase transition chemical equation for the equilibrium between liquid and gaseous phases Recall what the Second Law tells us about reaction free energy of chemical equilibria: If Δ G < 0 the reaction is spontaneous If Δ G > 0 the reverse reaction is spontaneous If Δ G = 0 the system is at equilibrium What does this tell us about equilibrium between liquid and gaseous phases?? Below the boiling point you know the gas condenses and turns into a liquid. This is, the reverse reaction is spontaneous and
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Unformatted text preview: Δ G > 0 Above the boiling point the liquid evaporates and turns into a liquid. I.e. the forward reaction is spontaneous and Δ G < 0 At exactly the boiling point, liquid and gas are in equilibrium and Δ G = 0 To calculate the boiling point you just need to calculate the temperature at which Δ G = 0 Estimate Δ H by setting it equal to the difference between the standard formation enthalpy Δ H ⁰ f of liquid and gaseous states Estimate Δ S by setting it equal to the difference between standard entropies S of liquid and ⁰ gaseous states...
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This note was uploaded on 01/24/2012 for the course CHEM 152 taught by Professor Chiu during the Fall '08 term at University of Washington.

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