Free energy coupling of electron and ion transfers across a Liquid-liquid interface is treated theoretically assuming electroneutrality of each phase and complete dissociation of electrolytes. A general method is presented for calculating the equilibrium inner potential difference between the two phases and equilibrium concentrations of redox species, as well as other ionic components from given initial concentrations, values of standard electrode potential of redox couples, and of standard ion transfer potential of other ionic components. The ion-electron exchange across the interface is exemplified for several simpler cases. The volume ratio has a dramatic effect on the equilibrium. The partition of indifferent-electrolyte ions can drive the redox reactions before the onset of electrolysis and can significantly alter the initial conditions for electron transfer studies at the liquid-liquid interface.