For a general reaction of the type A + 4B � 3C + 2D, in which A, B, C, and D are chemical substances, the heat of reaction can be calculated from DH⁰ = 3DH⁰_C + 2DH⁰_D - DH⁰_A - 4DH⁰_B, in which DH⁰_C is the heat of formation of Compound C from its elements in their standard states.

For example, if the reaction is the oxidation of glucose by nitrate, as is carried out by some nitrate-respiring bacteria

5C₆H₁₂O₆+24KNO₃ � 6CO₂+24KHCO₃+12N₂+18H₂O

then the heat of reaction is obtained from the following combination of heats of formation of products and reactants:




Tables of standard heats of formation can be found in the CRC Handbook of Chemistry and Physics, in Lange's Handbook of Chemistry. With such tables, the heats of all reactions involving the compounds can be calculated, including reactions that never have been carried out, or that for various reasons we cannot carry out easily in the laboratory.