Editing Standard enthalpy of formation (section)

== Key concepts for enthalpy calculations ==
*When a reaction is reversed, the magnitude of Δ''H'' stays the same, but the sign changes.
*When the balanced equation for a reaction is multiplied by an integer, the corresponding value of Δ''H'' must be multiplied by that integer as well.
*The change in enthalpy for a reaction can be calculated from the enthalpies of formation of the reactants and the products
*Elements in their standard states make no contribution to the enthalpy calculations for the reaction, since the enthalpy of an element in its standard state is zero. [[Allotropy|Allotropes]] of an element other than the standard state generally have non-zero standard enthalpies of formation.