Finding membrane potential equation using the Nernst equation? - Chemistry Stack Exchange most recent 30 from chemistry.stackexchange.com 2019-09-19T14:54:08Z https://chemistry.stackexchange.com/feeds/question/58465 https://creativecommons.org/licenses/by-sa/4.0/rdf https://chemistry.stackexchange.com/q/58465 4 Finding membrane potential equation using the Nernst equation? Aurges https://chemistry.stackexchange.com/users/34478 2016-09-04T14:53:51Z 2017-02-02T05:35:46Z <p>I am very new to electrochemistry and ion selective electrodes. The membrane potential of an ion selective electrode is given by $$E=\frac{RT}{nF}\ln{\frac{c_2}{c_1}}$$ Where R is universal gas constant, T temperature in kelvin, n the number of electrons transfered, F Faraday of electricity, $c_2$ the concentration of internal standard solution and $c_1$ is the concentration of the ion to be calculated. </p> <p>But according to the Nernst equation $$E= E^\circ -\frac{RT}{nF}\ln k$$ Can someone explain how to come up with the membrane potential equation using the Nernst equation?</p> https://chemistry.stackexchange.com/questions/58465/-/58470#58470 1 Answer by Li Zhi for Finding membrane potential equation using the Nernst equation? Li Zhi https://chemistry.stackexchange.com/users/32390 2016-09-04T16:42:06Z 2017-01-03T04:41:41Z <p>The Nernst Equation is $E = E^\circ - \frac{RT}{nF} \ln{Q_c}$. From that you can derive the approximation you gave. $Q_c$ <em>is</em> the product of the activities of the products over those of the reactants. This can be, for dilute solutions where activity approximates concentration, the typical [B]/[A] for the reaction A→B. So, the only thing you need to "explain" is why E° would be zero. Review the definition of E°. hint:What is ln(1/1)? See the discussion on concentration cells in: <a href="http://www.chem1.com/acad/webtext/elchem/ec4.html" rel="nofollow noreferrer">http://www.chem1.com/acad/webtext/elchem/ec4.html</a> </p>