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Enthalpies of Formation
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| Submitted: Mon Nov 10 2003
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Enthalpies of Formation Using Hess's Law we can calculate reaction enthalpies for a variety of reactions using tables of known enthalpies Many experimentally determined enthalpies are listed by the type of process DH for converting various liquids to the gas phase are listed in tables of enthalpies of vaporization DH for melting solids to liquids are listed in tables of enthalpies of fusion DH for for combusting a substance in oxygen are listed in tables of enthalpies of combustion The enthalpy change associated with the formation of a compound from its constituent elements is called the enthalpy of formation (DHf ) Conditions which influence enthalpy changes include: temperature pressure state of reactants and products (s, g, l, aq) The standard state of a substance is the form most stable at 298 °K (25 °C, or standard "room temperature") and 1 atmosphere (1 atm) of pressure When a reaction occurs with all reactants and products...
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