## Cell Electrode Potentials

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

- If the

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

- Calculate the potential for the following cell at room temperature:
Zn|Zn

^{2+}(0.1 M) || Cu^{2+}(0.2 M) | Cuwhere at 25 °C

Cu

^{2+}+ 2e^{-}→ Cu ;*E°*= 0.337 VZn

^{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.

- Chem.LibreTexts.org (2015). Cell EMF.
- NIST (2006). The International System of Units (SI) - Conversion Factors for General Use. Nist Special Publication 1038.
- Wikipedia (2017). Nernst Equation.

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