lecture6

0 kj 120 j 19 kj 62 enthalpy and calorimetry enthalpy

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Unformatted text preview: 1.3 J/(L atm) = -120 J ∆E = q + w = (2.0 kJ) + (-120 J) = 1.9 kJ 6.2 Enthalpy and Calorimetry Enthalpy H = E + PV where E = internal energy of the system P = pressure of the system V = volume of the system Since internal energy, pressure, and volume are all state functions, enthalpy is also a state function. H = E + PV. Therefore ∆H = ∆E + ∆(PV) for a process at constant pressure, ∆(PV) = P∆V so ∆H = ∆E + P∆V 6-2 Chapter 6 Thermochemistry at constant P, ∆E = qp + w = qp – P∆V (subscript p means P is constant), so ∆H = qp - P∆V + P∆V = qp ∆H = qp H can be thought of as the heat content of the system, ∆H = heat flow For processes which occur at constant volume, ∆V = 0 so w = 0, therefore ∆E = qP Enthalpy Changes in Chemical Reactions In an exothermic reaction, chemical potential energy is converted into thermal energy which is released to the surroundings as a positive heat flow. In an endothermic reaction, thermal energy absorbed from the surroundings is converted into chemical potential energy which results in a negative heat flow. For a reaction reactantsÆ products ∆H = Hproducts - Hreactants ∆H>...
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This note was uploaded on 04/05/2014 for the course CHEM 1211 taught by Professor Jackduff during the Spring '13 term at SPSU.

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