SLec9 - Lecture 9: Thermochemistry Variation of the...

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We can easily evaluate the reaction enthalpies at different temperatures, taking into account the following facts If we integrate this formula over T , we obtain the reaction enthalpies at T This is the Kirchhoff’s law Variation of the reaction enthalpy Δ H with temperature Lecture 9: Thermochemistry
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We can visualize the formula as follows Δ H(T 2 ) differs from Δ H(T 1 ) by a different heat absorbtion of reactants and products (upon reaction we heat them – not included in Δ H(298.15) ), i.e. reactants release heat absorbed along the path from T 1 to T 2, , but products absorb a different heat in order to go from T 1 to T 2. Example: esterification at 750 K of acetic acid with ethanol giving ethylacetate
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When the reaction takes part at different pressures, we can use the formulas But the variation with pressure is small (only non-ideal gas has it) In total, we have Variation of Δ H with pressure
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We can do the same in solutions The difference is that we must include the standard enthalpies in solution
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This note was uploaded on 09/23/2010 for the course CHEM 342 taught by Professor Prestonsnee during the Spring '08 term at Ill. Chicago.

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SLec9 - Lecture 9: Thermochemistry Variation of the...

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