Cell Potential Calculator

Calculate standard cell potential E-cell from reduction potentials: E-cell = E-cathode - E-anode. Determine if electrochemical cell is spontaneous and find Gibbs free energy.

⚡ Electrochemistry📐 E°cell = E°cathode - E°anode🧪 Chemistry

E° cathode reduction potential (V)

E° anode reduction potential (V)

n (moles of electrons transferred)

Please enter valid values.

Formula & Reference

Variable	Symbol	Formula	Units
Cell Potential Calculator	See formula	E°cell = E°cathode - E°anode	V

Step-by-Step Examples

Example 1

Zinc-Copper Cell (Daniell Cell)

E0(Cu^2+/Cu)=+0.340 V (cathode), E0(Zn^2+/Zn)=-0.763 V (anode), n=2.

E0cell = +0.340 - (-0.763) = +1.103 V
dG0 = -2 x 96485 x 1.103 = -212,900 J = -212.9 kJ
Spontaneous: E0 > 0

✓ E0cell = +1.103 V (spontaneous)

Example 2

Iron-Copper Cell

E0(Cu^2+/Cu)=+0.340 (cathode), E0(Fe^2+/Fe)=-0.440 (anode), n=2.

E0cell = 0.340 - (-0.440) = +0.780 V
dG0 = -2 x 96485 x 0.780 = -150,517 J = -150.5 kJ

✓ E0cell = +0.780 V

Example 3

Non-Spontaneous Cell

E0(Zn/Zn^2+)=-0.763 as cathode, E0(Cu/Cu^2+)=+0.340 as anode. Reversed from Daniell cell.

E0cell = -0.763 - 0.340 = -1.103 V
dG0 = -2 x 96485 x (-1.103) = +212.9 kJ
Non-spontaneous: requires electrical input (electrolysis)

✓ E0cell = -1.103 V (requires energy input)

Real-World Applications

🔋

Battery Design

Cell potential determines battery voltage. Series cells add voltages. 1.5 V AA uses Zn/MnO2.

🔧

Corrosion Protection

Galvanic corrosion occurs when E0 difference drives electron flow. Less noble metal corrodes.

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Chlor-Alkali Process

Industrial electrolysis of brine. E0cell = -2.19 V means minimum 2.19 V required.

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Analytical Electrochemistry

Voltammetry uses cell potentials to identify and quantify redox-active species.

Common Mistakes to Avoid

⚠️

Cathode minus anode, not reversed

E0cell = E0(cathode) - E0(anode). Both use REDUCTION potentials. Do not flip the anode sign twice.

⚠️

Always use reduction potentials

Standard tables list reduction potentials. Do not convert anode to oxidation potential separately; just use E0cell = Ecathode - Eanode.

⚠️

dG0 = -nFE0

F = 96,485 C/mol. n = moles of electrons. E must be in volts. dG in joules (divide by 1000 for kJ).

Frequently Asked Questions

What determines which is cathode and anode? ▾

Cathode: reduction (higher E0 reduction potential). Anode: oxidation (lower E0 reduction potential). E0cell = Ecathode - Eanode > 0 for spontaneous cell.

How is E0cell related to K? ▾

E0cell = (RT/nF)*ln K = (0.05916/n)*log K at 25 C. If E0cell=1.103 V, n=2: log K = 2*1.103/0.05916 = 37.3; K = 10^37.3.

What is EMF? ▾

Electromotive force = E0cell = maximum potential difference between electrodes. Measured when no current flows (open circuit voltage).

How are batteries connected? ▾

Series: voltages add. Parallel: current capacity adds, voltage stays same. A 12 V car battery = 6 cells x 2 V each (Pb-acid).

What is the relationship between E0cell and dG0? ▾

dG0 = -nFE0cell. Spontaneous: dG0 < 0 means E0cell > 0. Non-spontaneous: dG0 > 0 means E0cell < 0.

Related Chemistry Calculators

Formula Explorer connections

Interpretation: This formula links electron transfer, charge, potential, current or ionic transport in an electrochemical system. Assumption: Balance electron count and half-reactions, preserve sign conventions, and use consistent concentration, temperature and electrical units. Real cells include losses and overpotential.

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