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# enthalpy and calorific value

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1. hey so enthalpy=internal energy+volumn displacement work=(Cp)*(deltaT)

is there a way to calculate internal energy directly using a formula?

how does the calorific value of a substance tie in with enthalpy?
2. Indeed the enthalpy H=U+PV=integral[(Cp)dT] where H is the enthalpy, U is the internal energy, P is the pressure, V the volume, Cp the specific heat capacity at constant pressure and T the temperature.

The internal energy can be calculated from a formula using statistical mechanics, however this can be quite involved. For simple systems such as an ideal gas or a spin system the solution is straightforward but it can get rather complicated.

The calorific value of a substance is essentially the energy that is released upon burning the substance. This ties in with the enthalpy of combustion.
3. beautiful thanks

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Updated: June 6, 2012
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