The motive unit [MU] is the variable SI unit in which the motive entity (transformant) of a transformation is expressed, which depends on the energy transformation under study and on the chosen format. Fundamental MU for electrochemical transformations are:
- MU = x, for the particle or molecular format, N
- MU = mol, for the chemical or molar format, n
- MU = C, for the electrical format, e;
For the protonmotive force the motive entity is the proton with charge number z=1. The protonmotive force is expressed in the electrical or molar format with MU J/C=V or J/mol=Jol, respectively. The conjugated flows, I, are expressed in corresponding electrical or molar formats, C/s = A or mol/s, respectively.
The charge number, z, has to be considered in the conversion of motive units (compare Table below), if a change not only of units but a transition between the entity elementary charge and an entity with charge number different from unity is involved (e.g., O2 with z=4). The ratio of elementary charges per O2 molecule (zO2=4) is multiplied by the elementary charge (e, coulombs per electron), which yields coulombs per O2 [C∙x-1]. This in turn is multiplied with the Avogadro constant, NA (O2 molecules per mole O2 [x∙mol-1]), thus obtaining for ze∙NA the ratio of elementary charges [C] per amount of O2 [mol-1]. The conversion factor for O2 is 385.94132 C∙mmol-1.
Communicated by Gnaiger E 2018-10-20
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