Question #44848

The electrochemical reduction of an organic reactant \ce{R} occurs at a catalytic electrode of area $A$ in a cell of volume $V$ at a constant applied potential. The rate of disappearance of \ce{R} in the bulk solution is given by $r = -\frac{d[\ce{R}]}{dt} = k_{app} [\ce{R}]^n$. The reaction proceeds via the initial reversible adsorption of \ce{R} onto the electrode surface, followed by a rate-determining electron transfer step. The enthalpy of adsorption is $\Delta H_{ads}$ ($\Delta H_{ads} < 0$).

Under Condition I (low $[\ce{R}]$), the surface coverage of \ce{R} follows the Henry adsorption isotherm. The apparent rate constant is $k_I$. Under Condition II (high $[\ce{R}]$), the electrode surface is completely saturated with \ce{R}. The apparent rate constant is $k_{II}$.

Which of the following correctly identifies the units of $k_I$ and $k_{II}$, and the relationship between the apparent activation energy ($E_{a,app}$) and the true activation energy of the electron transfer step ($E_{a,true}$) under Condition I?