= Solution
The <midpoint potential> $E_m$ characterizes the redox couple under specified solution conditions: it is the potential at which oxidized and reduced forms have equal activities, or equal concentrations in the corresponding formal-potential convention. For a reversible cyclic voltammogram it is estimated by $(E_{pa}+E_{pc})/2$. It approximates the formal redox potential when the usual reversibility and <diffusion> assumptions apply; it is not the potential halfway along a scan chosen arbitrarily.
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