In: Chemistry
From the enthalpies of formation of various compounds involved in a chemical reaction it is possible to calculate the enthalpy or enthalpy of this reaction. Consider the overall reaction of reagent A with reagent B, to give a product C and product D.
The enthalpy of this reaction, being a state function, the enthalpy is less enthalpy final state of the initial state, that is, the enthalpy of formation of the products minus the enthalpy of formation of the reactants. As the enthalpy of formation are standardized to one mole of compound formed, we multiply these enthalpies of formation for the corresponding stoichiometric coefficients of each compound:
and how:
And, in general, it can be expressed as follows:
Which it is the formula used generally for calculation of the energy of a chemical reaction from the values of enthalpy of formation of the reactants and products.
for example: