Backup of Lab 04 new - INTRODUCTION Objective To determine...

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Objective To determine the factor RT F from diffusion potential measurements by using a caution permeable membrane. To determine the transport number of cautions and anions by using a cellophane membrane. 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 ∆Φ ------------------ ( 1 ) Gibbs energy arising from the concentration difference is :- G = R T ln C C 2 1 ------------------ ( 2 ) At equilibrium G = 0 and therefore :- G = G e + G c = 0 ∆Φ = RT zF ln C C 2 1 ---------------- ( 3 ) The cautions 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
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This note was uploaded on 11/07/2010 for the course CHEMICAL E 300 taught by Professor Ahmedghazal during the Spring '10 term at King Fahd University of Petroleum & Minerals.

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Backup of Lab 04 new - INTRODUCTION Objective To determine...

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