The Nernst Equation relates the reduction potential of an electrochemical reaction to the standard electrode potential, temperature, and activities of the chemical species undergoing oxidation and reduction.
Use this for $2H^+ + 2e^- \rightarrow H_2$ reactions ($E^0 = 0$).
Our calculators use a smartParser to handle scientific notation.
10^5 means 10510*1 means 10 multiplied by 1.1.8e-5 means 1.8 × 10-5| Half-Reaction | $E^0$ (V) |
|---|---|
| $Li^+ + e^- \rightarrow Li$ | -3.04 |
| $Zn^{2+} + 2e^- \rightarrow Zn$ | -0.76 |
| $2H^+ + 2e^- \rightarrow H_2$ | 0.00 |
| $Cu^{2+} + 2e^- \rightarrow Cu$ | +0.34 |
| $Ag^+ + e^- \rightarrow Ag$ | +0.80 |
| $F_2 + 2e^- \rightarrow 2F^-$ | +2.87 |
The equation functions as a bridge between thermodynamics and electrochemistry. It determines the maximum potential a battery can generate based on the concentration of its electrolytes. As reactants are consumed, $Q$ increases, causing $E$ to drop until the cell reaches equilibrium ($E = 0$).
In modern research, the Nernst Equation is vital for:
1. What happens to $E$ when concentrations are equal?
If [Products] = [Reactants], $Q=1$ and $\log(1)=0$, so $E = E^0$.
2. Can the Nernst potential be negative?
Yes, if the concentration gradient is strong enough to reverse the spontaneous direction of the cell.
3. Why is 0.0592 used in some versions?
It represents the value of $(2.303 \times RT) / F$ at exactly 25°C.
4. Does temperature affect the cell potential?
Yes, as $T$ increases, the effect of the concentration ratio on the potential becomes more significant.
5. What is $Q$ in the Nernst equation?
It is the reaction quotient, calculated as the activity of products divided by reactants.
6. Is Nernst equation applicable to gases?
Yes, by using partial pressures ($P$) instead of molar concentrations.
7. How is it used in biology?
To calculate the equilibrium potential for specific ions like $K^+$ across a cell membrane.
8. What is the value of Faraday's constant?
Approximately 96,485 Coulombs per mole of electrons.
9. Does it work for non-standard states?
That is its primary purpose: determining potential under any concentration/pressure.
10. What is $E^0$?
The standard reduction potential measured at 1M concentration and 1 atm pressure.
11. Why do batteries "die"?
Because concentrations change until $Q$ reaches a value where $E = 0$ (Equilibrium).
12. Can I use this for concentration cells?
Yes. In concentration cells, $E^0$ is 0, and the potential is driven purely by the Nernst term.
13. Is the equation accurate for high concentrations?
At high concentrations, activities should be used instead of molarity for better accuracy.
14. How many electrons ($n$) should I use?
Use the total number of electrons exchanged in the balanced redox half-reaction.
15. Does it assume ideal behavior?
Yes, the basic form assumes ideal solution behavior; corrections use activity coefficients.
16. Why is natural log ($\ln$) sometimes $\log_{10}$?
Chemists often use $\log_{10}$ by multiplying the $\ln$ term by 2.303 for easier mental calculation.