Electrolysis Calculator
Find the mass deposited or produced during electrolysis from current, time, molar mass, and valence, using Faraday's law of electrolysis.
⚡ What is Electrolysis?
Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction, most commonly depositing a metal onto an electrode (electroplating) or breaking a compound apart into simpler substances (such as splitting water into hydrogen and oxygen). This calculator applies Faraday's first law of electrolysis to find exactly how much mass is deposited or produced at an electrode from the current, time, molar mass, and valence you supply.
Electrolysis has widespread real-world use: electroplating jewelry, tableware, and connectors with copper, silver, gold, nickel, or chromium for appearance and corrosion resistance, refining and purifying metals like copper and aluminum on an industrial scale, and producing hydrogen gas by splitting water, an increasingly important process in clean energy. Chemistry students also use this exact calculation to verify lab electroplating results against theoretical predictions.
A common misconception is that more current or more time always deposits proportionally more mass without limit. That is true in Faraday's ideal formula, since mass is directly proportional to total charge (current multiplied by time), but real cells lose some current to side reactions like hydrogen gas evolution, so an actual deposit is often somewhat less than this calculator's theoretical prediction, especially at high current density.
This calculator is useful because manually converting time to seconds, looking up or remembering the Faraday constant (96,485 C/mol), and keeping track of which valence applies to which ion are all easy places to make an arithmetic slip. Selecting a common substance preset, or entering your own molar mass and valence, removes that friction and gives an instant, correct result.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Copper Electroplating
2 A for 30 minutes, copper (M=63.546 g/mol, n=2).
Example 2 — Silver Plating
5 A for 1 hour, silver (M=107.868 g/mol, n=1).
Example 3 — Aluminum Refining
10 A for 2 hours, aluminum (M=26.982 g/mol, n=3).
❓ Frequently Asked Questions
🔗 Related Calculators
What is Faraday's law of electrolysis?
Faraday's first law of electrolysis states that the mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electric charge passed through the electrolyte, m = ItM / (nF), where I is current, t is time, M is molar mass, n is the number of electrons transferred per ion, and F is the Faraday constant.
How do you calculate the mass deposited during electrolysis?
Multiply current by time to get total charge in coulombs, Q = It. Divide by n times the Faraday constant (96,485 C/mol) to get moles deposited. Multiply moles by molar mass to get the mass in grams, m = (It / nF) x M.
What is the Faraday constant?
The Faraday constant, F = 96,485 coulombs per mole, is the total electric charge carried by one mole (6.022 x 10^23) of electrons. It converts between charge measured in coulombs and the amount of chemical change measured in moles.
What does the valence number (n) mean in this formula?
n is the number of electrons gained or lost when one ion is converted to the neutral atom or molecule at the electrode. For copper(II), Cu2+ + 2e- -> Cu, n = 2. For silver, Ag+ + e- -> Ag, n = 1. For aluminum, Al3+ + 3e- -> Al, n = 3.
How much copper is deposited by 2 amps for 30 minutes?
Charge Q = 2 A x 1,800 s = 3,600 C. Moles = 3,600 / (2 x 96,485) = 0.018656 mol. Mass = 0.018656 x 63.546 g/mol = about 1.19 grams of copper deposited.
Why does electroplating use direct current (DC), not alternating current?
Electrolysis requires a one-directional flow of charge to consistently drive reduction at the cathode and oxidation at the anode. Alternating current would reverse the reaction on every half-cycle, depositing and then immediately re-dissolving the metal, resulting in essentially no net deposit.
Does time need to be in seconds for this formula?
Yes, the Faraday constant is defined in coulombs per mole, and coulombs are amps multiplied by seconds, so time must be converted to seconds before multiplying by current. This calculator accepts seconds, minutes, or hours and converts automatically.
What is the difference between Faraday's first and second law?
Faraday's first law says mass deposited is proportional to charge passed (used directly in this calculator). Faraday's second law says that for a fixed amount of charge, the mass of different substances deposited is proportional to their equivalent weight (molar mass divided by valence), comparing different substances under the same charge.
Can this formula be used for gas production, not just metal deposition?
Yes. The same formula applies to any electrode reaction with a known valence, including gas-producing reactions like hydrogen evolution (2H+ + 2e- -> H2, n = 2 per H2 molecule) or oxygen evolution at the anode. Enter the gas's molar mass and the number of electrons per molecule formed.
Why might my actual electroplated mass differ from the calculated value?
Real electrolysis cells are rarely 100% efficient, some current is diverted into side reactions such as hydrogen gas evolution at the cathode instead of metal deposition. This means the theoretical mass from Faraday's law is usually an upper bound on what actually deposits.
How is total charge related to current and time?
Charge in coulombs equals current in amperes multiplied by time in seconds, Q = It. This is the same relationship used in basic circuit analysis, electrolysis simply uses that charge to drive a specific quantity of chemical change at each electrode.