π Electrolysis Calculator
Faraday's law: mass, charge, current, time.
How to Use This Calculator
Choose what to solve for, enter current, time, molar mass, and electrons per ion. Adjust efficiency for real-world plating.
Faraday's Law
F = 96,485 C/mol | Q = I x t
Each mole of electrons carries one faraday of charge. Dividing total charge by n x F gives moles of metal, times molar mass gives grams. Efficiency accounts for side reactions that waste current.
Worked Example
Copper plating at 2 A for 30 min, 100 percent efficient: Q = 2 x 1800 = 3,600 C. m = 3600 x 63.55 / (2 x 96485) = 1.19 g of copper.
Electroplating in Practice
Chrome bumpers, gold jewelry, and copper circuit boards are all made by electrolysis. The object to be plated becomes the cathode, and metal ions from solution deposit onto it atom by atom. Platers control current and time precisely because Faraday's law links charge directly to metal thickness. Too much current gives rough, burnt deposits; too little wastes time.
Efficiency Is Never 100 Percent
Side reactions like hydrogen evolution at the cathode steal current, so real processes run at 90 to 98 percent efficiency. This calculator gives the theoretical maximum; multiply by your process efficiency for realistic planning. Industrial cells also lose energy to resistance heating, which is why aluminum smelting consumes enormous electricity.
Aluminum Production
The Hall-Heroult process makes aluminum by electrolyzing alumina dissolved in cryolite at nearly 1000 C, consuming about 13 kWh per kilogram of metal. This enormous energy cost is why recycling aluminum saves 95 percent of the energy: remelting skips electrolysis entirely. Your soda can is mostly recycled for this reason.
Water Electrolysis
Splitting water into hydrogen and oxygen needs 1.23 V theoretically, but real cells run at 1.8 to 2.0 V because of overpotential at the electrodes. Green hydrogen projects use renewable electricity for this process. The 2:1 volume ratio of hydrogen to oxygen produced is a direct, visible confirmation of Faraday's law.
Frequently Asked Questions
What is Faraday's law of electrolysis?
The mass deposited is proportional to charge passed: m = (Q x M) / (n x F), where Q is coulombs, M molar mass, n electrons per ion, and F = 96,485 C/mol. Double the current or time, double the metal.
How long does it take to plate 1 gram of copper?
Copper needs 2 electrons per atom (63.55 g/mol). Charge = 1 x 2 x 96485 / 63.55 = 3,037 C. At 2 amps that is about 25 minutes. This calculator runs these numbers instantly.
What is a Faraday?
One mole of electrons, equal to 96,485 coulombs of charge. Passing one faraday through Cu2+ solution deposits half a mole of copper (31.8 g) because each copper ion needs 2 electrons.
Why is my electroplating slower than calculated?
Current efficiency is rarely 100 percent. Side reactions like hydrogen evolution steal current, especially at high current density. Industrial plating runs 90 to 98 percent efficient; hobby setups often 70 to 90.
Can this calculate gas volumes from electrolysis?
Yes. Convert moles of electrons to moles of gas (H2 needs 2 e-, O2 needs 4 e-), then use 24.5 L/mol at room temperature. Water electrolysis at 2 A for 1 hour makes about 0.93 L of H2.