Mole (unit) in chemistry as a convenient way to express amounts of reactants and products of chemical reactions. For example, the chemical equation can be interpreted to mean that 2 mol dihydrogen (H) and 1 mol dioxygen (O) react to form 2 mol water (HO). The mole may also be used to represent the number of atoms, ions, or other entities in a given sample of a substance. The concentration of a solution is commonly expressed by its molarity, defined as the amount of dissolved substance per unit volume of solution, for which the unit typically used is moles per litre (mol/l).
Epoxy epoxy resins is the epoxide group content. This is correctly expressed as the specific amount of substance of epoxide groups in the material B under consideration, calculated as the ratio of the amount of substance of epoxide groups in this material B, "n"(EP), divided by the mass "m"(B) of the material B under consideration, in this case, the mass of the resin. The SI unit for this quantity is "mol/kg", or multiples thereof. Deprecated quantities which are still in use are the so-called "epoxide number" which is (not a number and should therefore not be referred to as such, but)