# Reactants' Standard Enthalpy of Formation

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Equation / Last modified by mike on 2015/07/30 06:22
(Delta H_f^0)_"reactants" =
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MichaelBartmess.Reactants' Standard Enthalpy of Formation
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The reactants' total Standard Enthalpy of Formation,DeltaH_f^0, is a component of the Standard Enthalpy of Reaction, DeltaH_r^0, along with the products' total Standard Enthalpy of Formation.

Reactants' Standard Enthalpy of Formations (DeltaH_f^0) = sum_"reactants" v_i * (DeltaH_f^0)_i .

• v_i - stoichiometric coefficient for "reactant"_i
• (DeltaH_f^0)_i - Standard Enthalpy of Formation for "reactant"_i

This equation allows you to sum Standard Enthalpy of Formation for up to ten reactants.

# Notes

Enthalpy, H, of the system is equal to the internal energy of the system, U,  plus the product of pressure and volume of the system, PV.  The enthalpy of a homogeneous systems is proportional to the size of the system. For various molecular substances the specific enthalpy can be specified as H/m, where M is mass.

The Standard Enthalpy of Reaction is the enthalpy change (change in chemical potential energy of the system) that occurs when one mole of matter undergoes a chemical reaction under standard conditions.  The Standard Enthalpy of Reaction is typically measured in units of kJ/mole. Likewise the Standard Enthalpy of a Formation is also measured typically in kJ/mole.

The Standard Enthalpies of a Formation, DeltaH_f^0, are computed under standard conditions that include:

• standard temperature - 25 degrees C
• standard pressure (for gases) - 1 atmosphere
• standard Molar concentration (for solute in an ideal solution) - 1 M
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