*Cell Electrode Potentials *

## Cell Electrode Potentials

Easily solve the Cell Electrode Potential (Electromotive Force, EMF) equation for a missing term.
Instructions

- The Electromotive Force (EMF) equation, also known as the Cell Electrode Potential equation, consists of two known constants,
*R* and *F*, and five experimental terms.
- Given all but one of the experimental terms, this tool solves for the missing one.
- To use the tool, one of its form fields must be left empty.
- To empty a field, just double click it.
- If no field is left empty, the tool will randomly empty one and recompute its value based on the values of the other fields.

What is computed?

- The Nernst Equation given above relates the electromotive force of an electrochemical half- or full-cell reaction to the Standard Electrode Potential, temperature, activities of reactant and products, and number of electron transferred during the net redox (reduction and oxidation) reaction (Chem.LibreTexts.org, 2015; Wikipedia, 2017) where
*R* is the gas constant defined as 8.3144598(48) J·K^{-1}·mol^{-1}.

*F* is the Faraday constant defined as 96485.33289(59) C·mol^{-1}.

*E* is the electromotive force in Voltz (V).

*E°* is the standard electrode potential in Voltz (V).

*T* is the temperature in the Kelvin scale.

*n* is the number of electrons transferred during the net redox reaction.

*Q*_{eq} is a reaction quotient or ratio of reactants and product activities (often approximated by concentrations).

Important Notes

If *T* is in Celsius, Fahrenheit, Rankine, or other units, it must be converted to kelvins. We have developed a Temperature Converter tool that simplifies all these conversions.

Units conversions

When changing units, you may want to follow NIST 2006 guidelines for expressing results to a given number of significant digits:

- If the
**first** significant digit of the converted value is **greater than or equal** to the **first** significant digit of the original value, round the converted value to the **same** number of significant digits as there are in the original value.
- If the
**first** significant digit of the converted value is **smaller** than the **first** significant digit of the original value, round to **one more** significant digit.

Who can use this tool?

- Lab techs as well as chemistry teachers and their students.

Suggested Exercises

- Calculate the potential for the following cell at room temperature:
Zn|Zn^{2+} (0.1 M) || Cu^{2+} (0.2 M) | Cu

where at 25 °C

Cu^{2+} + 2e^{-} → Cu ; *E°* = 0.337 V

Zn^{2+} + 2e^{-} → Zn ; *E°* = -0.763 V

- How would you classify the above cell?
- galvanic
- electrolytic
- voltaic
- Daniell

- How would you classify the above cell?
- primary
- secondary
- reserve
- fuel

- Calculate the EMF of the above cell if one of the electrode solution is ten-fold diluted.
- Calculate the EMF of the above cell if both electrode solutions are ten-fold diluted.

References

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