EMF of Cell Formula:
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Definition: The electromotive force (EMF) of a concentration cell is the potential difference developed when two identical electrodes are immersed in solutions of the same electrolyte but different concentrations.
Purpose: This calculator helps determine the voltage generated by differences in ionic activity between two half-cells without ion transfer between them.
The calculator uses the Nernst equation for concentration cells:
Where:
Explanation: The natural logarithm of the activity ratio determines the potential difference between the two half-cells.
Details: Understanding concentration cell EMF is crucial in electrochemistry, battery technology, corrosion studies, and biological systems where concentration gradients exist.
Tips: Enter the temperature in Kelvin, cathodic ionic activity, and anodic ionic activity. All values must be positive numbers.
Q1: What's the difference between concentration and activity?
A: Activity is the effective concentration that accounts for non-ideal behavior in solutions, especially at higher concentrations.
Q2: Why is temperature important in this calculation?
A: The Nernst equation shows direct proportionality between EMF and absolute temperature.
Q3: What happens if the activities are equal?
A: The EMF becomes zero since ln(1) = 0, indicating no potential difference.
Q4: Can I use molarity instead of molality?
A: For dilute solutions, they're nearly equal, but molality (mol/kg) is preferred as it's temperature-independent.
Q5: What are typical values for this type of cell?
A: Concentration cells typically generate small voltages, often in the millivolt range.