Equilibrium potential for an ion is calculated using?

Chloride ions (Cl-) are present in higher concentration in the ECF than in the cell interior, and they tend to diffuse along this concentration gradient into the cell. The interior of the cell is negative relative to the exterior, and chloride ions are pushed out of the cell along this electrical gradient. An equilibrium is reached between Cl- influx and Cl- efflux. The membrane potential at which this equilibrium exists is the equilibrium potential. Its magnitude can be calculated from the Nernst equation, as follows: where ECl = equilibrium potential for Cl- R = gas constant T = absolute temperature F = the Faraday number (number of coulombs per mole of charge) ZCl = valence of Cl- (-1) = Cl- concentration outside the cell = Cl- concentration inside the cell Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 1. General Principles & Energy Production in Medical Physiology. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.