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Unformatted text preview: INTRODUCTION I-Objective:--To determine the factor RT F from potential by using permeable membrane.-To determine the ionic mobilities of cations and onions by using a cellophane membrane. II-Theory:- The potential difference which is known as the Nernst potential is two electrolyte solutions of different concentrations separated by a membrane. If we have two KCl solutions were separated by a cation permeable membrane, some K- ions cross from the more concentrated side to the less concentrated one, and as a result the left hand side will have a negative potential with respect to the other side, resulting in a Nernst potential which exactly balance the tendency of the concentration to become equal. The Gibbs energy difference, G e is :- G e = z F where, z = The charge on the permeable ions (z=1 in our case). Gibbs energy arising from the concentration difference is :- G = R T ln C C 2 1 At equilibrium G = 0 and therefore :- G = G e + G c = 0 = RT zF ln C C 2 1 The cations and anions of the electrolyte have different velocity, the faster ionic species initially diffuse first. The transport numbers of the ions are calculated from the velocity of the cations and anions :- t y y y + = + + +- , t y y y- = +- +- hence t + + t- = 1 t + and t- indicate what proportions of cation and anions' particles in the flow of current through the electrolyte. Thus, the diffusion potential D is :- D = (t +- t- ) D...
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