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Electrolysis Calculator

Chemistry

Calculate mass deposited or gas produced during electrolysis using Faraday's law: m = MIt/nF. Select element or enter custom molar mass, current, and time.

63.55 g/mol
g/mol
2
2 A
A
30 min
min

Mass Deposited

1.185
Moles Produced
0.019
Total Charge
3,600
Volume at STP (gas)
0

This calculator computes your Mass Deposited, Moles Produced, Total Charge, Volume at STP (gas) from the values you enter.

Inputs
SubstanceMolar Mass (custom only)Electrons per Formula Unit (custom only)CurrentTime
Outputs
Mass DepositedMoles ProducedTotal ChargeVolume at STP (gas)

What is a Electrolysis?

The Electrolysis Calculator determines the mass of metal deposited (or gas produced) during electrolysis using Faraday's law: m = MIt/(nF), where M is molar mass, I is current in amperes, t is time in seconds, n is the number of electrons transferred per formula unit, and F = 96,485 C/mol. Select a substance from the preset list (copper, silver, gold, zinc, nickel, iron, aluminium, H₂, O₂, Cl₂) or enter custom values.

Faraday's law is exact for ideal electrolysis: every electron that flows deposits or dissolves one (1/n)th of a mole of the target species. The law connects the macroscopic (current in amperes, time in seconds, mass in grams) with the molecular scale (Avogadro's number, elemental charge). This calculator implements both Faraday's laws — mass proportional to charge, and mass proportional to equivalent weight — in one unified formula.

For the reverse calculation (finding the current or time needed to deposit a target mass), rearrange: I = mF×n/(M×t) or t = mF×n/(M×I). The Cell EMF Calculator provides the thermodynamic context (minimum voltage needed) and the Nernst Equation Calculator accounts for concentration effects on the required voltage.

How to use this Electrolysis calculator

  1. Select the Substance from the dropdown. Copper and silver are most common in educational problems; hydrogen and oxygen for water electrolysis.
  2. For Custom substance: enter the Molar Mass (g/mol) and Electrons per Formula Unit (n).
  3. Enter the Current in amperes. Common lab electrolysis: 0.5–5 A. Industrial: 100–500,000 A.
  4. Enter the Time in minutes. The calculator converts to seconds internally (multiply by 60).
  5. Read Mass Deposited and Total Charge — verify with the known electrochemical equivalent for the element.

Formula & Methodology

Faraday's law of electrolysis:

m = M × I × t / (n × F) Q_charge = I × t    (coulombs) moles = Q_charge / (n × F)

Gas volume at STP:

volume_STP = moles × 22.414 L/mol

Worked example — copper electroplating:

Deposit copper from CuSO₄ solution: Cu²⁺ + 2e⁻ → Cu (M = 63.546 g/mol, n = 2). Current I = 2 A, time = 30 minutes = 1800 s.

Q = 2 × 1800 = 3600 C moles Cu = 3600 / (2 × 96485) = 3600 / 192970 = 0.01866 mol mass = 0.01866 × 63.546 = 1.186 g

At 2 A for 30 minutes, 1.19 g of copper is deposited — enough to coat a surface area of about 40 cm² with a 1 μm thick layer (copper density = 8.96 g/cm³). This is the type of calculation jewellery manufacturers and printed circuit board platers perform to set plating parameters.

Frequently Asked Questions

Electrolysis is the non-spontaneous decomposition of a substance by passing electrical current through it. An external power supply forces electrons to flow: at the cathode (negative electrode), cations are reduced (gain electrons); at the anode (positive electrode), anions are oxidised (lose electrons). Electrolysis is used to extract metals from ores, electroplate surfaces, produce industrial chemicals (Cl₂, NaOH via the chlor-alkali process), refine metals (electrolytic copper refining), and produce hydrogen by water splitting.
Faraday's first law: the mass of substance deposited or dissolved is proportional to the total charge passed: m ∝ Q (where Q = I × t, charge in coulombs). Faraday's second law: for the same charge, the masses deposited of different substances are proportional to their equivalent weights (M/n). Combined formula: m = MIt/(nF), where M is molar mass (g/mol), I is current (A), t is time (s), n is the number of electrons per ion, and F = 96,485 C/mol is Faraday's constant.
Select the substance being deposited or evolved (copper, silver, gold, zinc, nickel, iron, aluminium, hydrogen gas, oxygen gas, chlorine gas, or custom). Enter the current in amperes and the time in minutes. For custom substances, enter the molar mass and the number of electrons per formula unit. The calculator returns mass deposited (g), moles produced, total charge (C), and volume at STP for gases.
Faraday's constant F = 96,485 C/mol is the charge carried by one mole of electrons = N_A × e = 6.022 × 10²³ × 1.602 × 10⁻¹⁹ = 96,485 C. It means that to deposit one mole of a univalent ion (n=1, like Ag⁺ → Ag), you need 96,485 coulombs = 96,485 A·s. For a divalent ion (n=2, like Cu²⁺ → Cu), one mole of metal requires 2 × 96,485 = 192,970 C. For practical current (2 A), one mole of copper takes 192,970/2 = 96,485 seconds ≈ 26.8 hours.
This calculator assumes 100% current efficiency — all charge goes to the desired electrode reaction. In practice, competing reactions (hydrogen evolution, oxygen evolution, side reactions) reduce current efficiency to 70–95% for most industrial processes. Copper electrorefining achieves ~95% efficiency; aluminium smelting ~90%; industrial chlor-alkali ~95%. To account for current efficiency η%: multiply the calculator's mass by η/100. Current efficiency is determined empirically for each specific process.
India is a major producer of electrolytic metals. HINDALCO and NALCO produce aluminium via Hall-Héroult electrolysis (Al₂O₃ in molten cryolite, E ≈ 4–5 V, ~300–500 kA currents). Copper India (Vedanta) and Hindustan Copper produce electrolytic copper (99.99% pure). Hindustan Zinc uses electrolytic zinc refining. The chlor-alkali industry (Gujarat Alkalies, GACL, DCM Shriram) electrolyses brine to produce Cl₂ and NaOH — essential for India's PVC and chemical industries.
Electroplating deposits a thin metal coating on a substrate for corrosion protection, aesthetics, or wear resistance. The cathode (workpiece) gains metal; the anode (often the plating metal) dissolves. Mass deposited = MIt/(nF). For a gold-plated jewellery piece: plating 2 μm of gold (M = 196.97, n = 3) over an area of 50 cm², density of Au = 19.3 g/cm³: mass = 50 × 0.0002 × 19.3 = 0.193 g. Time at 0.5 A: t = m×n×F/(M×I) = 0.193 × 3 × 96485 / (196.97 × 0.5) = 565 s ≈ 9.4 minutes. The BIS (Bureau of Indian Standards) specifies minimum plating thicknesses for various applications.
The chlor-alkali process electrolyses concentrated NaCl brine: Cathode: 2H₂O + 2e⁻ → H₂(g) + 2OH⁻; Anode: 2Cl⁻ → Cl₂(g) + 2e⁻. Products: Cl₂ gas (anode), H₂ gas (cathode), NaOH solution. All three are commercially valuable: Cl₂ for PVC, disinfectants, and solvents; NaOH for aluminium production, paper, soap, and textiles; H₂ for ammonia synthesis. India's chlor-alkali capacity is approximately 4 million tonnes of NaOH per year, supporting the country's chemical industry.
Water electrolysis: 2H₂O → 2H₂ + O₂ (E°cell = −1.23 V; requires ≥1.23 V external voltage, typically 1.8–2.0 V with overpotentials). Cathode: 2H₂O + 2e⁻ → H₂ + 2OH⁻. Anode: 2OH⁻ → ½O₂ + H₂O + 2e⁻. Per 96,485 C (1 Faraday): 0.5 mol H₂ = 11.2 L at STP at cathode; 0.25 mol O₂ = 5.6 L at anode. India's National Green Hydrogen Mission targets 5 million tonnes per year of green hydrogen (electrolytic, from renewable electricity) by 2030 — requiring ~125 GW of electrolysis capacity.
Faraday's constant F = N_A × e = (Avogadro number) × (elementary charge). This relationship is how Avogadro's number was originally determined with high precision. By measuring the mass of silver deposited per coulomb (the electrochemical equivalent of silver = M/nF = 107.87/(1 × 96485) = 1.1180 mg/C), and knowing the charge of a single silver ion, N_A = F/e = 96485 / 1.602 × 10⁻¹⁹ = 6.022 × 10²³. Faraday's electrolysis experiments (1833) and Millikan's oil drop experiment (1909) together gave the first precise measurement of N_A.