Cell Potential Calculator
Determine the standard voltage ($E^\circ_cell$) and Gibbs Free Energy ($\Delta G^\circ$) of any electrochemical cell instantly.
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From the batteries in your phone to the plating on your jewelry, electrochemistry runs the modern world. Use our tool to predict voltages, calculate energy efficiency, and understand the flow of electrons in any redox system.
The Driving Force ($E^\circ$)
Every element has a specific "thirst" for electrons, called its Reduction Potential.
When you connect two different metals, the one with the higher potential "pulls" electrons from the other. This flow of electrons is electricity. The difference in pulling power is the Cell Potential (Voltage).
Free Energy ($\Delta G^\circ$)
Voltage tells you if a reaction can happen, but Gibbs Free Energy tells you how much work it can do.
Where $F$ is Faraday's Constant ($96,485\ C/mol$) and $n$ is moles of electrons.
How to Predict Spontaneity
Spontaneous (Galvanic)
- • $E^\circ_cell$ is Positive (+)
- • $\Delta G^\circ$ is Negative (-)
- • Produces Energy (e.g., Discharging Battery)
Non-Spontaneous (Electrolytic)
- • $E^\circ_cell$ is Negative (-)
- • $\Delta G^\circ$ is Positive (+)
- • Consumes Energy (e.g., Charging Battery)
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Frequently Asked Questions
What is Standard Cell Potential (E°cell)?
Standard Cell Potential ($E^\circ_{cell}$) is the voltage difference between the cathode (reduction half-cell) and the anode (oxidation half-cell) under standard conditions (1M concentration, 1 atm pressure, 25°C). It represents the maximum electromotive force (EMF) the cell can generate.
What constitutes a spontaneous reaction?
A reaction is spontaneous if $E^\circ_{cell}$ is positive. This corresponds to a negative Gibbs Free Energy ($\Delta G^\circ < 0$). Such reactions occur naturally in Galvanic (Voltaic) cells, like batteries discharging.
What is the formula for E°cell?
The formula is simply: $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$. You use the standard reduction potentials for both values directly from the table; the subtraction accounts for the oxidation at the anode.
How do I calculate Gibbs Free Energy from potential?
Use the relationship: $\Delta G^\circ = -nFE^\circ_{cell}$, where 'n' is the number of moles of electrons transferred, 'F' is the Faraday constant (96,485 C/mol), and 'E' is the cell potential.
What is the difference between Galvanic and Electrolytic cells?
In a Galvanic Cell, a spontaneous chemical reaction produces electricity ($E^\circ > 0$). In an Electrolytic Cell, electrical energy is used to drive a non-spontaneous reaction ($E^\circ < 0$), such as in electroplating or recharging a battery.
Why do we use a salt bridge?
A salt bridge allows ions to flow between the two half-cells to maintain electrical neutrality. Without it, charge would build up (positive at anode, negative at cathode) and the reaction would stop almost instantly.
Does multiplying a half-reaction change its E°?
No! Standard potential is an intensive property. If you multiply a half-reaction by 2 to balance electrons, the voltage ($E^\circ$) remains exactly the same. Only the Extensive properties (like $\Delta G$) are multiplied.
What is the Standard Hydrogen Electrode (SHE)?
The SHE is the universal reference point for all potentials. By definition, the potential of the reaction $2H^+ + 2e^- \rightarrow H_2$ is assigned a value of 0.00 V. All other potentials are measured relative to this.
How does concentration affect cell potential?
Standard potentials assume 1M concentrations. If concentrations deviate, use the Nernst Equation: $E = E^\circ - (RT/nF) \ln Q$. Generally, increasing reactant concentration increases voltage.
What acts as the Cathode vs Anode?
Remember 'Red Cat' and 'An Ox'. Reduction happens at the Cathode. Oxidation happens at the Anode. In a spontaneous cell, the element with the higher reduction potential is the cathode.