SLec8 - Lecture 8 Thermochemistry We will now study...

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Lecture 8: Thermochemistry We will now study thermodynamics in the presence of chemical reactions Consider first pure substances (nothing else) that are in a container and react under standard conditions (P=1 bar and usually T=298.15 K) Exothermic processes: -reactants have higher enthalpy then products -heat is released in the reaction and flows from the system to the surroundings, q P <0 Endothermic processes: -reactants have lower enthalpy then products -heat is absorbed in the reaction and flows from the surroundings to the system, q P >0
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The infinitesimally small change of enthalpy of a single substance is - partial molar enthalpy If the amount of this substance is changed (in a reaction with T, P =const), we have that We define standard molar enthalpy of formation Δ H f o (298.15) A for the substance A , when A is obtained at P=1 bar (T=298.15 K) in a reaction from elements in their (most common) standard states . Example:
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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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SLec8 - Lecture 8 Thermochemistry We will now study...

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