Cell potential, denoted as $E_{cell}$, is the measure of the electromotive force (emf) of an electrochemical cell. It represents the potential difference between the two electrodes.
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The standard cell potential ($E^\circ_{cell}$) is measured under standard conditions: 1 M concentration for solutions, 1 atm pressure for gases, and 25°C.
Cell potential can be calculated using the Nernst equation when conditions are not standard.
$E_{cell}$ is positive for spontaneous reactions and negative for non-spontaneous reactions.
The overall cell potential is the difference between the reduction potentials of the cathode and anode: $E_{cell} = E_{cathode} - E_{anode}$.
A galvanic (voltaic) cell operates with a positive $E_{cell}$, while an electrolytic cell operates with a negative $E_{cell}$.
Review Questions
What does it mean if a cell has a positive $E_{cell}$?
How do you calculate $E_{cell}$ under non-standard conditions?
What are the standard conditions for measuring $E^\circ_{cell}$?
Related terms
Electrode Potential: The voltage developed by a half-cell in an electrochemical cell relative to a standard reference electrode.
Nernst Equation: An equation that relates the cell potential to its standard potential and concentrations of reactants and products: $$E = E^\circ - \frac{RT}{nF} \ln Q$$.
Galvanic Cell: An electrochemical cell that derives electrical energy from spontaneous redox reactions occurring within the cell.