Nernst Equation Calculator

Created by Gabriela Diaz
Last updated: Nov 30, 2022

Use the Nernst equation calculator to determine the reduction potential E of cells or half-cells.

In electrochemistry, the Nernst equation is widely used to determine a cell's reduction potential E. Cells are devices that allow generating electrical current. This current generation is related to the reduction potential E of the cell. Hence, the greater the E of a cell, the greater the produced current.

Keep reading to find:

  • What is reduction potential?;
  • The cell potential equation or Nernst equation; and
  • How to calculate the potential of a cell with concentrations using the Nernst equation.

We have another tool related to electrochemistry, which we called the Randles-Sevcik equation calculator. Check it to learn more about this topic!

Reduction potential

The reduction potential, also known as the oxidation-reduction potential (ORP), is a measure of a chemical species' tendency to receive or lose electrons, that is, to be reduced or oxidize another chemical species. The greater the metal's reduction potential, the more likely it is to be reduced and act as an oxidant.

The reduction potential can be used to describe the potential of a half-cell or a full cell with metal electrodes. Some metals are more likely than others to lose electrons. This means that the electric current produced in a cell might be higher or lower depending on the metal of the electrode. Reduction potential is measured in volts (V) and relative to a reference electrode. The term voltage is explained in the Omni Calculator's Ohm's law calculator if you need it.

Nernst equation to calculate E of a cell — The cell potential equation

An electrochemical cell is a device that uses the energy generated in a redox reaction to generate an electric current. Here, the reduction occurs at the cathode and the oxidation at the anode. In these devices, it's of interest to know the reduction potential. To calculate the E of a cell the Nernst equation, also known as the cell potential equation, is used. The formula to calculate the E of a cell is:

E=E0R Tz F ln([ red ][ ox ])\small E = E_0 - \cfrac{R \ T}{z \ F} \ \ln\left( \cfrac{[\ \text{red} \ ]}{[ \ \text{ox} \ ]}\right)

where:

  • EE — Reduction potential, expressed in volts (V);
  • E0E_0 — Standard reduction potential, also expressed in volts (V);
  • RR — Gas constant, equal to 8.314 J/(K⋅mol);
  • TT — Temperature at which the reaction would occur, measured in Kelvins (K);
  • zz — Number of moles of electrons transferred in the reaction (mol);
  • FF — Faraday constant, equal to the number of coulombs per mole of electrons (96,485.3 C/mol);
  • [ red ][ \ \text{red} \ ] — Chemical activity of the molecule (atom, ion…) in the reduced form. It can be substituted by concentration; and
  • [ ox ][\text{ ox } ] — Chemical activity of the molecule (atom, ion…) in the oxidized form. It also can be substituted by concentration.

This is the equation that uses the Nernst equation calculator. You can use it to determine the potential E of half-cells or full cells. This tool allows calculating the potential of a cell with concentrations of the molecules.

The standard reduction potential E0E_0 of a material is a measure of its tendency to lose electrons. The standard reduction potential E0E_0 is measured under standard conditions: 25 °C, activity equal to 1 per ion, and pressure of 1 bar per gas involved in the reaction. The standard reduction potential is established relative to the standard hydrogen electrode (SHE), defined as the potential of 0 V.

If the metal electrodes of a cell have close reduction potentials, the current produced will be small, whereas if the difference is significant, the magnitude of the current will be large.

Gabriela Diaz
Standard red. potential (E₀)
V
Temperature
°F
Electrons transferred
mol
Activity (reduced form)
Activity (oxidized form)
Reduction potential (E)
V
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