Nernst Equation Calculator

Nernst Equation Calculator | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Science & Education
Input types: number, select
Output type: text
Sample coverage: 4
API ready: Yes

Overview

The Nernst Equation Calculator computes real cell and electrode potentials under non-standard conditions using the formula E = E⁰ − (RT/nF)·lnQ. By providing the standard potential, number of electrons transferred, reaction quotient, and temperature in Kelvin or Celsius, you instantly obtain the thermal factor RT/F, the Nernst correction term, the slope per decade of Q, the actual cell potential E, and the Gibbs free energy change ΔG.

When to use

Determining the non-standard voltage of an electrochemical or galvanic cell as reactants deplete and reaction quotient Q changes.
Evaluating ion-selective electrode potentials, pH sensor responses, or concentration cells across temperature variations.
Calculating the change in Gibbs free energy (ΔG = −nFE) for redox reactions at specified temperatures and concentrations.

How it works

1Enter the standard electrode or cell potential E⁰ in volts and specify the number of electrons transferred (n).
2Provide the reaction quotient Q representing the ratio of product to reactant activities or concentrations.
3Input the operating temperature and select whether the value is in Kelvin (K) or Celsius (°C).
4Review the resulting cell potential E, thermal voltage RT/F, per-decade slope (2.303RT/nF), and Gibbs free energy ΔG.

Use cases

Analyzing galvanic battery discharge curves by tracking voltage drop as the reaction quotient Q increases.
Calibrating potentiometric sensors and ion-selective electrodes using the theoretical millivolt response per decade of analyte activity.
Solving electrochemistry homework and lab calculations involving non-standard redox systems and concentration gradients.

Examples

1. Depleted Daniell Cell Potential

Chemistry Student

Background

A student is running a standard zinc-copper galvanic cell where the copper ion concentration has dropped significantly relative to zinc ions.

Problem

Calculate the operating cell voltage and Gibbs free energy when [Zn²⁺]/[Cu²⁺] reaches Q = 100 at 25 °C.

How to use

Set E⁰ to 1.10 V, n to 2, Q to 100, temperature to 298.15, and unit to K.

e0 = 1.1, n = 2, q = 100, temperature = 298.15, tUnit = K

Outcome

Cell potential drops by 59.16 mV to E = 1.04084 V, with ΔG = −200.85 kJ/mol.

2. One-Electron Potentiometric Sensor Response

Analytical Chemist

Background

A laboratory technician is evaluating the theoretical response slope for an ion-selective electrode sensitive to a monovalent ion at 25 °C.

Problem

Verify the expected potential change per 10-fold change in analyte concentration relative to zero baseline.

How to use

Set E⁰ to 0 V, n to 1, Q to 10, temperature to 25, and unit to C.

FAQ

What is the Nernst equation?

It is an electrochemical equation, E = E⁰ − (RT/nF)·lnQ, relating reduction potential to standard potential, temperature, electron count, and reaction quotient.

What is the 59.16 mV rule?

At 25 °C (298.15 K), the term 2.303·RT/F equals 59.16 mV, meaning a single-electron transfer shifts potential by 59.16 mV per decade change in Q.

How does temperature affect cell potential in this calculator?

Temperature scales the thermal voltage term RT/F, altering both the Nernst correction factor and the resulting Gibbs free energy ΔG.

Can I input temperature in Celsius?

Yes, you can choose Celsius (°C) or Kelvin (K) from the unit selector, and the calculator automatically handles conversion to absolute temperature.

How is Gibbs free energy calculated?

It is calculated using the relation ΔG = −nFE, where n is transferred electrons, F is the Faraday constant, and E is the calculated cell potential.

e0 = 0, n = 1, q = 10, temperature = 25, tUnit = C

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Depleted Daniell Cell Potential

2. One-Electron Potentiometric Sensor Response

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