MATHEMATICAL DISCUSSION OF THE APPLICATION OF HESS LAW

Let there be given a system of chemical reaction equations; a vanishin g linear combination of these reactions should be called a mechanism. Then Hess' law in thermochemistry states that the corresponding linear combination of the (known or unknown) reaction heats will also be zer o. If only so-called irreducible mechanisms are taken into account (wh ich is always the case in thermochemistry) then their number will be f inite and the mechanisms themselves can be determined by standard line ar algebraic methods. A straightforward numerical example is shown lan d criteria are presented whether or not such a mechanism exists when s earching for the unknown heat of reaction in a given problem.