Faraday's Law of Electrolysis Calculator

Faraday’s First and Second Laws of Electrolysis state:

1. The mass of substance deposited is proportional to the charge passed
2. The mass deposited per coulomb is proportional to the equivalent weight of the substance

Combined formula:

m = (M × I × t) / (n × F)

Where:

• m = mass deposited (grams)
• M = molar mass of the element (g/mol)
• I = current (amperes, A)
• t = time (seconds)
• n = number of electrons per ion (oxidation state)
• F = Faraday constant = 96,485 C/mol

Also: Q = I × t (charge in coulombs)

Common electrolysis targets:

Hydrogen and oxygen evolution: At the cathode in water electrolysis: 2H₂O + 2e⁻ → H₂ + 2OH⁻ At the anode: 2H₂O → O₂ + 4H⁺ + 4e⁻ For each mole of H₂: 2 moles of electrons (193,000 C). For each mole of O₂: 4 moles (386,000 C).

That 2-to-4 split is why water electrolysis gives you twice the volume of hydrogen as oxygen. Same current through both electrodes, same charge, but oxygen costs twice as many electrons per molecule. For gases the calculator also converts moles to litres at 25 °C and 1 atm, where one mole occupies 24.45 L.

Industrial applications:

• Copper refining: electrolytic purification to 99.999% purity
• Aluminum production (Hall-Héroult process): 15 kWh per kg of Al
• Electroplating: thin metal coatings for corrosion resistance and appearance
• Chlor-alkali process: NaCl electrolysis to produce Cl₂ and NaOH