Cathodic Ionic Activity Formula:
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Definition: Cathodic Ionic Activity is the measure of the effective concentration of a molecule or ionic species in a cathodic half-cell.
Purpose: This calculator determines the activity of ions in the cathodic electrolyte of a concentration cell with transference, accounting for valencies of ions.
The calculator uses the Nernst equation modified for transference:
Where:
Details: Accurate ionic activity calculations are essential for understanding electrochemical cell behavior, predicting reaction rates, and designing batteries and corrosion protection systems.
Tips: Enter all required parameters including EMF, ion counts, valencies, transport number, temperature, and anodic activity. All values must be positive numbers.
Q1: What is the transport number of an anion?
A: It's the fraction of total current carried by the anion in the electrolyte (typically between 0 and 1).
Q2: Why does temperature affect ionic activity?
A: Temperature influences ion mobility and the equilibrium between ion pairs and free ions in solution.
Q3: What are typical values for ionic activity?
A: For dilute solutions, activity approaches concentration (mol/kg). For concentrated solutions, activity coefficients typically range from 0.1 to 1.5.
Q4: How do I determine the number of positive/negative ions?
A: This depends on your electrolyte's dissociation. For NaCl, it would be 1 (Na+) and 1 (Cl-), so enter 1.
Q5: What if my transport number is unknown?
A: Typical values are 0.4-0.6 for many salts. Consult literature for your specific electrolyte.