BasicThermodynamics 1.4

# BasicThermodynamics 1.4 - Heat of formation and phase...

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Heat of formation and phase transformations + Δ = Δ M m 2 T 298 gas , O p solid , M p solid , MO p 298 T dT c 2 1 c c H H If the temperature of interest is higher than the melting temperatures for both the metal and its oxide, the enthalpy change for M liquid + ½ O 2 gas = MO liquid is then + Δ + T T gas , O p liquid , M p liquid , MO p MO m MO m 2 dT c 2 1 c c H + + Δ MO m M m 2 T T gas , O p liquid , M p solid , MO p M m dT c 2 1 c c H Gaskell, Chapter 6.4

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MSE 3050, Thermodynamics and Kinetics of Materials, Leonid Zhigilei Heats of Reactions –Hess’s Law Heat absorbed or released in a given chemical reaction occurring under constant pressure conditions is the same weather the process occurs in one or several steps (Hess, 1840). Example: C (graphite) + O 2 (gas) = CO 2 (gas) Q = -393.6 kJ mol -1 C (graphite) + ½ O 2 (gas) = CO (gas) Q = - 110.5 kJ mol -1 CO (gas) + ½ O 2 (gas) = CO 2 (gas) Q = -283.1 kJ mol -1 Total: -393.6 kJ mol -1 ¾
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## This note was uploaded on 02/14/2012 for the course MSE 3050 taught by Professor Zhigilei during the Spring '12 term at UVA.

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BasicThermodynamics 1.4 - Heat of formation and phase...

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