Nernst equation Definition and 22 Threads

In electrochemistry, the Nernst equation is an equation that relates the reduction potential of a reaction (half-cell or full cell reaction) to the standard electrode potential, temperature, and activities (often approximated by concentrations) of the chemical species undergoing reduction and oxidation. It was named after Walther Nernst, a German physical chemist who formulated the equation.

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  1. J

    Nernst Equation with Pressure Differences

    I'm working with the Nernst equation with pressure differences right now: ## E = E_t + \frac{RT}{nF}ln ((P/P_0)^{\Delta \eta_G})## I'm assuming pure reactants here so, so I'm omitting the product terms: ##\frac{\Pi_{products} x_i ^{\nu_i}}{\Pi_{reactants} x_i ^{\nu_i}}## which would normally...
  2. A

    The Nernst Equation- I apologize in advance for my ignorance

    Ecell = E0cell - (RT/nF)lnQ So I understand the Nernst Equation, but I don't have some info. (Please bare with me, I'm in secondary) I'm doing a Cu - Al cell. My E cell is negative (-1.33). Does this have an affect on the equation? What exactly does E0 stand for? I understand how to find E...
  3. Teemo

    Standard Reduction Potential Changes in Regards to Acidity

    Homework Statement The reduction of O2 to H2O in acidic solution has a standard reduction potential of +1.23 V. What is the effect on the half-cell potential at 25 °C when the pH of the solution is increased by one unit? O2(g) + 4H+(aq) + 4e- –> 2 H2O(l) (A) The half-cell potential...
  4. H

    Nernst equation - Lambda Sensor

    Hello everyone, I am not sure if this question is comfortable in the chemistry section but I will try my luck. I have been dealing with lambda sensors a little bit and when I look at the characteristic voltage lambda curve I keep asking myself why it flatens out when getting into the rich...
  5. D

    Cell Potential with Nernst Equation

    Homework Statement Homework Equations Nernst Equation where Q = [product]/[reactants], R = 8.314, F = 96500 The Attempt at a Solution I got E° to be 0.012 V because E° of cathode - E° of anode. -0.131 - (-0.143) = 0.012. The balanced equation I got was: Pb2+ + Sn → Pb + Sn2+ For the values of...
  6. T

    Limitations of the nernst equation

    Oh hi there, first post. I'm looking into electrochemical cells and using to the nernst equation to predict cell potential values, and came across a few threads on the topic already on this forum (although none really answered my question), so thought this would be the place to ask. I know...
  7. somasimple

    Is the Nernst equation limited to dilute ionic solutions?

    Hi All, From this page: http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Electrochemistry_4%3a_The_Nernst_Equation and this paragraph: The Nernst equation works only in dilute ionic solutions Does it mean that the Nernst equation is only accurate for solutions where...
  8. B

    Nernst equation and equilibrium constant

    The equation ΔG=-nFEcell, I understand. I also understand that, at unity activities of all species, Q=1 so R*T*ln(Q)=R*T*ln(1)=0. And therefore Ecell=E°cell and ΔG=ΔG°. However, surely we cannot then write that ΔG°=-nFE°cell=-R*T*ln(K), since ΔG° is measured at unity activity when Q=1, rather...
  9. M

    Calculating Ecell and Voltage Across a Galvanic Cell | Nernst Equation Problem

    Homework Statement Consider a Galvanic cell made of two half cells: Ag+ + e− → Ag(s) +0.799 V Cd2+ + 2e− → Cd(s) − 0.403 V (a) Calculate the open circuit potential, when the concentration of Ag+ 0.08 mol and the concentration of the Cd2+ is 0.8 mol. (b) Calculate the voltage across the...
  10. A

    Why is Mixing Units in the Nernst Equation Considered Accurate?

    One thing that always puzzled me on the Nerst equation is that you may mix the units of concentration and pressure. This, however, seems to be rather arbitrary. How can using the units of mol/L and atm in the same equation result in accurate results? It seems to be rather arbitrary...
  11. T

    Can the Nernst Equation Determine Missing Sodium Concentrations?

    A rather tame ltxnsp was recently found on Easter Island by a retired neurophysiologist. He reported the following measurements of ECF and ICF concentrations (in millimoles): ICF ECF Pr+ 0 150 Na+ ? ? K+ 10 100 Cl- 109 250 HCO3- 1 10 so this is the question: He lacked the proper...
  12. R

    Calculating E(cell) and Ratio of [Ni^2+]/[Zn^2+] in a Zn-Ni Cell

    Homework Statement For a cell in which the reaction Zn(s)+ Ni^2+(aq)->Ni(s)+ Zn^2+(aq) calculate the E(cell) when [Ni^2+]=0.05M, [Zn^2+]=0.85M. Then, find the ratio of [Ni^2+]/[Zn^2+], when the cell is "flat" Homework Equations The simplified nernst equation ...
  13. Z

    Calculating 'n' in Nernst Equation for Fe3+ and I- Reaction

    Homework Statement How do I find out the 'n' of Nernst Equation for this reaction? 2Fe3+ + 3I- -------> 2Fe2+ + I3-
  14. G

    Electrochemical Cells, Cell Potentials: Using Nernst Equation

    Homework Statement The standard reduction potentials for Ni2+ and Sn2+ are as follows: Ni2+ + 2e− → Ni E° = −0.23 V Sn2+ + 2e− → Sn E° = −0.14 V Calculate the equilibrium constant at 25°C for the reaction Sn2+(aq) + Ni(s)→ Sn(s) + Ni2+(aq) Homework Equations Nernst...
  15. P

    Calculating Cell Potential Using Nernst Equation for Ag+ Voltaic Cell

    This problem is homework from a lab I did yesterday. Normally I would just ask my TA, but since it's homework I can't. I could email him, but I feel like I'll probably get a faster response if I post this here Homework Statement Use the Nernst equation to determine the cell potential for...
  16. G

    What prevents infinite potential with Nernst Equation

    The nernst equation has a log Q term. The denominator of that could be very close to zero. That would make Q close to infinity and log Q close to infinity. How high can the EMF be due to concentration in the real world and why?
  17. U

    Calculate Ecell using Nernst Equation and Appendix D Data | Mg-Al Cell Problem

    Homework Statement Use the Nernst equation and data from Appendix D in the textbook to calculate E cell for each of the following cells. Mg(s)|Mg+2 (0.012 M) || [Al(OH)4]- (0.25M), OH- (0.048M)|Al(s) Homework Equations Ecell = Ecell(standard) - 0.0591/n * log Q The Attempt...
  18. G

    Redox potential (Using the Nernst Equation)

    The redox midpoint potential (Eo’) of NAD+/NADH at pH 7.0 is -320 mV. If the total concentration of {[NAD+] + [NADH]} is 1.5 mM in cells, and the cellular redox potential is about -200 mV, what are the concentrations of [NAD+] and [NADH], respectively? Under certain oxidative stress...
  19. G

    What Is the Voltage of This Voltaic Cell at 298 K with Given Concentrations?

    Homework Statement Electrochemistry - Nernst Equation Pb2+ + 2 e- → Pb (s) ξo = -0.13 V Ag+ + 1 e- → Ag (s) ξo = 0.80 V What is the voltage, at 298 K, of this voltaic cell starting with the following non-standard concentrations: [Pb2+] (aq) = 0.08 M [Ag+] (aq) = 0.5 M Homework...
  20. U

    Nernst Equation Applied to Half-Reactions

    [SOLVED] Nernst Equation Applied to Half-Reactions The Nernst equation can be applied to half-reactions. Calculate the reduction potential (at 25°C) of the half-cell Cu/Cu2+ (1.9×10-4 M). (The half-reaction is Cu2+ + 2e- --> Cu. E° = 0.34 V) 0.34-[ (8.314)(298)/ (2)(96485)] *...
  21. H

    Verifying Nernst Equation Calculation: Pb2+ and Ag+

    Can anyone check if I am doing this right? Given: Pb2+ + 2e- ---> Pb(s) E standard = -0.13V Ag+ + 1e- ---> Ag(s) E standard = 0.80V [Pb2+] = 0.05M [Ag+] = 0.5 M these are non standard concentrations Temp = 298K Using the Nernst equation, find E My answer: Pb...
  22. Monique

    Some help with the Nernst equation?

    Nernst equation: \DeltaG = -2.3 RT log10 \frac{C_o}{C_i} + zFV R = 1.98x10-3 kcal/°K mole T = absolute temperature in °K (37°C= 310 °K) Co= concentration dissolved compound outside of cell Ci= concentration dissolved compound inside of cell z = the charge of the dissolved compound to...
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