CSU Sacramento, C 133

Excerpt: ... rent + time how to relate G to electrical potential component definitions for galvanic cells line notation to express redox reactions in cells standard reduction potential derivation of the Nernst Equation application of the Nernst Equation relating K (equilibrium constant) to E [last topic not covered and not on final due to lack of time] Covered today Applications of The Nernst Equation Examples: Determine the voltage for a Ag/AgCl electrode when [Cl] = 0.010 M if E = 0.222 V? The following electrode, Pb(s)|PbF2(s)|F is used to determine [F]. It is paired with a reference electrode that has an E value of 0.197 V (vs. the S.H.E.) with the reference electrode connected to the + end of the voltmeter. If E for the above reduction reaction is 0.350 V, and the measured voltage is 0.268 V, what is [F]? Electrochemistry Applications of The Nernst Equation Application of Nernst Equation is most common in potentiometry In potentiometry Electrochemistry measured volta ...

University of Texas, CH 302

Excerpt: ... u+ + 2e$ Eo (reduction) = 0.339V Nis Eo (reduction) = -0.236V = -0.575 = net Cathode Ni+ Now use the equation Eo = (-0.236V) - (0.339V) Cathode - anode Note that AS WRITTEN, this reaction is not spontaneous. However we can reverse the reaction and Eo = +0.575 and the reaction is spontaneous. Cu+ + Nis $ Cus + Ni+ (spontaneous ) COMPLICATION: THE NERNST EQUATION If electrochemistry was simply a matter of calculating Eo values, life would be easy. But it is not. Do you really think that if we put together a nickel and copper cell and measured the potential, it would be 0.575? If you do, you are probably the same sort of person who believes that the pH of a 0.01M HCl solution is 2 (Go measure it, it is not.) In fact, there are a lot of complications to solution chemistry that need to be addressed if we are going to get a reasonable quantitative handle on the actual potential of an electrochemical cell. We need to deal with CONCENTRATION and how it affects E. We will borrow what we learned back i ...

Winona, COURSE1 1

Excerpt: ... Name _ Study Sheet for Cell Biology 308 Instructions: Print out a copy of this sheet. Write your name in the upper right hand corner. Provide HAND WRITTEN answers or drawings to all questions. Do not use a computer to write answers to these questions. Turn in at the beginning of class as indicated on the schedule. Draw a cartoon of the structure of a typical motor neuron. Label the dendrites, cell body, axon hillock, axon, Schwann cells and bulb termini. What gives rise to the resting membrane potential? What is the relationship between the Na/K pump and the membrane potential? Write the Nernst Equation . Consider the Nernst Equation . What variables determine the calculated value of the membrane potential? When can you use the Nernst Equation ? What does the Goldman equation do that the Nernst Equation does not do? What is the relationship between ion channels and changes in the membrane potential? What is measured by patch clamping? How does the structure of the Na+ channel differ from ...

Caltech, CH 24

Excerpt: ... Biophysical Chemistry Chemistry 24a Winter Term 2008 Instructor: Sunney I. Chan Lecture 22 March 10, 2008 Electrochemical equilibria. Nernst equation . Electrochemical equilibria: moving electrons and ions moving down potential gradient >0 <0 + + <0 >0 Oxidation-reduction reaction: An oxidation-reduction reaction is one in which different atoms or molecules gain or lose electron(s) during a reaction, that is, their oxidation states change. For an ion, it is often straightforward to assign the oxidation state, as it is given by the ionic charge. The higher the oxidation state, the more oxidized the atom is, while the lower the oxidation state, the more reduced it is. Hence, oxidation and reduction can be considered as loss and gain of electrons, respectively. A simple oxidation-reduction (redox) reaction: Zn0 + Cu2+ Zn2+ + Cu0 This reaction could be written as a sum of the following electron transfer reactions: Zn0 Zn2+ + 2 eCu2+ + 2 e- Cu0 Example of a biologically important redox molecule Cytochrom ...

Rochester, CHEM 132

Excerpt: ... of 298 K and 1 Molar concentrations. We can use the current we generate from a galvanic cell to do electrical work. 2. Our previous relationships involving G will therefore be useful to us, including Hess Law and the dependence of G on pressures (concentrations). Specifically, we expand our use of G = G0 + RTlnQ where Q is the reaction quotient, to derive the dependence of cell potential (battery voltage) E on concentration. The result is the Nernst equation , E = E0 (0.0592/n)log10Q. 3. One implication of the Nernst equation is that we can make working galvanic cells where the half reactions at the anode and cathode involve the same reaction running in opposite directions. These are called concentration cells and rely on entropic rather than energetic driving forces. 4. The Nernst equation also gives us a relationship for the equilibrium constant for a reduction oxidation reaction that tells us how far it will go. In other words, we can determine how much current we can draw before the battery ...

Georgetown, MATH 200

Excerpt: ... ubility Equilibria Applications in Equilibria Problem Solving 7 8 6 PIB lab, Lecture 13 (by default lectures 9-12 too) Read 16.1-16.5. Exp 20 and Problems 16.41-49 odd, 16.50 17.37-40 (these are limiting reactant stoichiometry probs). Read 17.1-17.3. Exp 25 and problems 17.41-17.44 Mar 25, 27, 28 Apr 1, 3, 4 Read 17.4. Ksp lab and problems 17.45-17.55 odd 15.35-49 odd, 16.81,83,85 and 17.17-27 odd Apr 8, 10, 11 Electrochemistry Odd sections: voltaic cells, Nernst Equation Even sections: electrolytic cells and electrolysis No Quiz: Tue prep for exam 3, Thur & Fri Exam 3 returned during recitation Electrochemistry Even sections: voltaic cells, Nernst Equation Odd sections: electrolytic cells and electrolysis 9 Exp 16 and problems 20.83, 85, 89, 90, 105 or Exp 17 and problems 20.2537 odd, 49, 55-60. Apr 15, 17, 18 Apr 22, 24, 25 10 Exp 16 and problems 20.83, 85, 89, 90, 105 or Exp 17 and problems 20.2537 odd, 49, 55-60. ...

University of Illinois, Urbana Champaign, CHEM 104

Excerpt: ... ond, if we think back to our discussion on thermodynamics, we should recall that G = w max. This allows us to relate thermochemistry to electrochemistry using the following equation: Go = w max = -nFE for a system at standard conditions. Most of the batteries and Galvanic Cells we will be considering will not be at standard conditions, so we need to consider Gibbs Free Energy at non-standard conditions. Recall that: G = Go + RT ln(Q) 1 Chemistry 104 B/D Lecture Reviews Lecture #11 Because G = -nFE cell, we can now substitute as follows: -nFE cell = -nFEocell + RT ln(Q) Rearranging gives the Nernst Equation : o E cell = E cell RT ln (Q ) nF Where Ecell is the non-standard cell potential, Eocell is the standard cell potential, R is the gas constant, T is the temperature in K, n is the number of moles of electrons in the cell, F is Faradays constant, and Q is the reaction quotient. The Nernst Equation is a powerful tool for us as chemists! It allows us to look at the potential of cell ...

UC Davis, NPB 100

Excerpt: ... Resting Membrane Potential Lectures What you will learn in these lectures 1. You will learn that all cells, including neurons, have a resting membrane potential. 2. You will learn that two conditions are necessary to produce a voltage across a cell membrane (CM). 1) There must be a concentration difference for at least one species of ion across the CM. 2) The membrane must also be permeable to at least one species of ion. 3.You will learn that two forces will act on ions. 1) A chemical diffusion force and 2) an electrical force. 4.You will learn that a charge difference (voltage) is created across the CM as a result of the chemical and electrical forces. 5.You will learn how to quantify the magnitude of the chemical and electrical forces acting on ions. 6.You will learn that the Nernst equation can be used to predict the potential across the CM for a particular species of ion. 7.You will learn that the Nernst equation is insufficient to predict the voltage across a membrane permeable to multiple ions. 8.You w ...

Toledo, BIO 310

Excerpt: ... Announcements: Last lecture 1. Organization of the nervous system 2. Introduction to the neuron Today electrical potential 1. 2. 3. 4. Generating membrane potential Nernst equation Goldman equation Maintaining ionic distributions Neural Signaling A Simple Circuit Within neurons Between neurons electrical chemical & electrical Bioelectric Potentials Neurons have an electrical potential (voltage) across the cell membrane The inside of the cell is more negative than the outside called the Resting Membrane Potential Measuring Membrane Potential amplifier microelectrode Reference electrode 0 mV Resting potential cell -80 mV Bathing solution time Electrophysiology techniques Silver / Silver chloride wire electrode Amplifier output Reference electrode 3M KCl solution Glass micropipette Very tiny hole (<0.1m) Resting Membrane Potential How is it generated? 1. differential distribution of ions inside and outside the cell 1. Selective Permeability of the membrane to some ions ...

University of Texas, CH 302

Excerpt: ... + Cu+ + Nis Break it down into the half cell reactions: Anode Cus + 2eCu+ + 2e Eo (reduction) = 0.339V Nis Eo (reduction) = -0.236V Cathode Ni+ Now use the equation Eo = (-0.236V) - (0.339V) Cathode - anode = -0.575 = net Note that AS WRITTEN, this reaction is not spontaneous. However we can reverse the reaction and Eo = +0.575 and the reaction is spontaneous. Cu+ + Nis Cus + Ni+ (spontaneous ) COMPLICATION: THE NERNST EQUATION If electrochemistry was simply a matter of calculating Eo values, life would be easy. But it is not. Do you really think that if we put together a nickel and copper cell and measured the potential, it would be 0.575? If you do, you are probably the same sort of person who believes that the pH of a 0.01M HCl solution is 2 (Go measure it, it is not.) In fact, there are a lot of complications to solution chemistry that need to be addressed if we are going to get a reasonable quantitative handle on the actual potential of an electrochemical cell. We need to deal ...

N.C. State, CH 331

Excerpt: ... sign convention) affects other measures of electrical properties, notably transmembrane current, which are all expressed inside with respect to outside. Thus our current convention is that current crossing the membrane from inside to outside is positive. In physics we express the potential as V (unit is the volt). In chemistry the Nernst equation is used to describe the dependence of the oxidation potential on concentration. The symbol is E (or Eo) and the unit is also the volt. The Nernst equation The Nernst equation describes the potential for each half-reaction a(Ox) + neThe electrode potential is given by: b RT ln [Red] E=E a nF [Ox] o b(Red) The standard potential (i.e. potential at 1 molar concentration) is Eo. where R is the gas constant and F is the Faraday (96,450 J/volt). In an electrochemical cell where two half-reactions are combined to make a redox reaction, the electromotive force is: emf = E(+) - E(-) The free energy is G = -nFE. Therefore, the standard free energy change for a redox pro ...

N.C. State, CH 331

Excerpt: ... Using the outside as the reference potential makes sense as all cells share that outside. This choice of direction (or sign convention) affects other measures of electrical properties, notably transmembrane current, which are all expressed inside with respect to outside. Thus our current convention is that current crossing the membrane from inside to outside is positive. In physics we express the potential as V (unit is the volt). In chemistry the Nernst equation is used to describe the dependence of the oxidation potential on concentration. The symbol is E (or Eo) and the unit is also the volt. 4 The Nernst equation The Nernst equation describes the potential for each half-reaction a(Ox) + neThe electrode potential is given by: [Red] b o E = E RT ln a nF [Ox] Application of the Nernst equation to membrane potential The free energy per mole of solute moved across the membrane Gconc = -RTln(Co/Ci) where Co is the concentration outside the membrane and Ci is the concentration inside the membrane. The ...