The electrochemistry cell calculator computes cell potential, Gibbs free energy, equilibrium constant, and Nernst equation corrections for non-standard conditions. Select anode and cathode half-reactions from 30+ standard reduction potentials.
Half-Reactions
Cell Results
How to Use the Electrochemistry Cell Calculator
The electrochemistry cell calculator determines the voltage output of any galvanic cell using standard reduction potentials. It also calculates the Gibbs free energy change (ΔG) and equilibrium constant (K) to tell you if the cell reaction is thermodynamically favorable.
Step 1: Select Anode and Cathode
The anode is the electrode where oxidation occurs — it has the more negative standard reduction potential. The cathode is where reduction occurs — it has the more positive standard reduction potential. For the Daniell cell, select Zn²⁺/Zn as the anode (-0.76 V) and Cu²⁺/Cu as the cathode (+0.34 V).
Step 2: Calculate Standard Conditions
The standard cell potential is: E°_cell = E°_cathode - E°_anode. For the Daniell cell: E°_cell = +0.34 - (-0.76) = +1.10 V. A positive E°_cell means the reaction is spontaneous at standard conditions (1 M concentration, 298 K, 1 atm).
Step 3: Apply Nernst Equation (Optional)
For non-standard concentrations or temperatures, enable the Nernst toggle and enter the actual ion concentrations. The Nernst equation is: E = E° - (RT/nF) × ln(Q). At 298 K: E = E° - (0.0257/n) × ln(Q), where Q = [anode ion]/[cathode ion] for simple M/M²⁺ couples.
Understanding the Results
The ΔG value uses ΔG = -nFE_cell. For the Daniell cell with n=2: ΔG = -2 × 96485 × 1.10 = -212 kJ/mol. The equilibrium constant K is found from ln(K) = nFE°/RT. For 1.10 V and n=2 at 298 K: K ≈ 10^37 — meaning the reaction strongly favors products. The cell notation Zn|Zn²⁺||Cu²⁺|Cu describes the physical setup: anode on the left, double bar for the salt bridge, cathode on the right.
Galvanic vs. Electrolytic Cells
A galvanic cell (E_cell > 0) does work spontaneously — batteries and fuel cells. An electrolytic cell (E_cell < 0) requires external electrical energy to drive the reaction — electroplating, aluminum smelting, water electrolysis. The same cell can operate in both modes depending on whether an external voltage is applied.
FAQ
How do you calculate cell potential (E_cell)?
E_cell = E_cathode - E_anode, where both potentials are standard reduction potentials. The cathode is where reduction occurs (more positive E°), the anode is where oxidation occurs (more negative E°). A positive E_cell means the reaction is spontaneous.
What is the Nernst equation?
The Nernst equation corrects cell potential for non-standard conditions: E = E° - (RT/nF) × ln(Q). At 25°C this simplifies to E = E° - (0.0257/n) × ln(Q), or using log₁₀: E = E° - (0.0592/n) × log(Q), where n is electrons transferred and Q is the reaction quotient.
What is the Daniell cell?
The Daniell cell is the classic galvanic cell: Zn anode in ZnSO₄ solution, Cu cathode in CuSO₄ solution, connected by a salt bridge. E_cell = E°(Cu²⁺/Cu) - E°(Zn²⁺/Zn) = +0.34 - (-0.76) = +1.10 V. It's the historical basis for the modern battery.
How is ΔG related to cell potential?
ΔG = -nFE_cell, where n is moles of electrons transferred, F is Faraday's constant (96485 C/mol), and E_cell is in volts. A positive E_cell gives negative ΔG (spontaneous). At equilibrium, ΔG = 0 and E_cell = 0.
Is this electrochemistry calculator free?
Yes, completely free with no signup required. All calculations run in your browser.
What determines if a galvanic or electrolytic cell?
A galvanic (voltaic) cell has E_cell > 0 and releases electrical energy spontaneously. An electrolytic cell has E_cell < 0 and requires external electrical energy to drive the non-spontaneous reaction (like electroplating or electrolysis).
How does temperature affect cell potential?
The Nernst equation includes temperature (T in Kelvin). Higher temperature increases thermal noise and can shift equilibrium. The standard potential E° itself has a small temperature dependence, but at near-ambient temperatures the dominant effect is through the RT/nF term in the Nernst equation.