Electrolysis calculator: mass deposited and plating time
This electrolysis calculator follows OpenStax Chemistry: charge Q = I·t, moles of electrons n = Q/F, then moles and grams of metal. Example: 2 A for 60 minutes deposit 2.371 g of copper from a Cu²⁺ solution.
Example: Calculate: mass deposited · Metal (ion): copper Cu²⁺ (z = 2) · Current I 2 A · Time t 60 min → Result: Deposited mass 2.371 g. Source: OpenStax Chemistry 2e, 17.7 Electrolysis: Q = I·t and Q = n·F; Example 17.9 10.23 A for 1 h → 36,830 C → 0.3817 mol e⁻ → 41.19 g Ag; Al³⁺ 25.0 A, 15.0 min → 2.10 g Al; Example 17.10 chromium plating 33.46 A → 11.0 h (read 10.10.2026). Updated: .
How it is calculated
Faraday’s law in three steps: Q = I·t, n(e⁻) = Q/F, n(metal) = n(e⁻)/z. OpenStax Chemistry explains it like this: the current I (ampere = coulomb per second) multiplied by the time gives the charge Q; dividing by the Faraday constant F = 96,485.33 C/mol gives the moles of electrons; the half-reaction tells how many electrons z one ion needs. Multiply by the molar mass and you have the mass: m = I·t·M / (z·F).
Examples from OpenStax
| Process | Data | Result |
|---|---|---|
| Silver plating, Ag⁺ + e⁻ | 10.23 A, 1 h | 36,828 C → 0.3817 mol e⁻ → 41.17 g Ag |
| Aluminium, Al³⁺ + 3e⁻ | 25.0 A, 15.0 min | 0.0777 mol → 2.10 g Al |
| Chromium plating, Cr³⁺ + 3e⁻ | 237 g Cr, 33.46 A | 10.95 h |
| Copper, Cu²⁺ + 2e⁻ | 2 A, 60 min | 2.371 g Cu |
OpenStax gets 41.19 g of silver because it rounds to 36,830 C and 107.9 g/mol; with the CIAAW atomic weight 107.87 g/mol the calculator shows 41.17 g. For the chromium layer the book rounds to 11.0 h. The charge numbers z come from the half-reactions in OpenStax Appendix L: Ag⁺ needs one electron, Cu²⁺, Zn²⁺ and Ni²⁺ need two, Cr³⁺, Al³⁺ and Au³⁺ three. Gold can also be deposited from Au⁺ (z = 1) – then choose “enter molar mass and z”.
Time for a given mass
Turn the formula around: t = m·z·F / (M·I). Twice the current halves the time; a metal with z = 2 needs twice the charge of one with z = 1 for the same number of atoms. Molar masses of other substances come from the molar mass calculator; the cell voltage under non-standard conditions is calculated with the Nernst equation calculator.
Frequently asked questions
What is the formula for mass deposited in electrolysis?
m = I·t·M / (z·F): current times time gives the charge, divided by F = 96,485.33 C/mol and by z gives the moles of metal, times M gives grams.
How much copper do 2 A deposit in one hour?
About 2.371 g: 7,200 C ÷ 96,485.33 C/mol = 0.0746 mol e⁻, halved for Cu²⁺ = 0.0373 mol, times 63.546 g/mol.
What is the Faraday constant?
The charge of one mole of electrons: 96,485.332 12 C/mol, an exact value according to NIST CODATA.
How long does it take to deposit 237 g of chromium at 33.46 A?
About 10.95 hours (OpenStax rounds to 11.0 h): 4.558 mol Cr × 3 electrons × F = 1.32 × 10⁶ C.
Why is my real mass smaller?
The calculation assumes that the whole charge deposits the metal. Any charge used by other electrode reactions is missing from the metal.
What does z mean?
The number of electrons one ion takes up: 1 for Ag⁺, 2 for Cu²⁺, 3 for Al³⁺. It comes from the half-reaction.
Sources and legal basis
- OpenStax Chemistry 2e, 17.7 Electrolysis: Q = I·t and Q = n·F; Example 17.9 10.23 A for 1 h → 36,830 C → 0.3817 mol e⁻ → 41.19 g Ag; Al³⁺ 25.0 A, 15.0 min → 2.10 g Al; Example 17.10 chromium plating 33.46 A → 11.0 h (read 10.10.2026)
- OpenStax Chemistry 2e, Appendix L Standard Electrode (Half-Cell) Potentials: Ag⁺ + e⁻, Cu²⁺ + 2e⁻, Zn²⁺ + 2e⁻, Ni²⁺ + 2e⁻, Cr³⁺ + 3e⁻, Al³⁺ + 3e⁻, Au³⁺ + 3e⁻ (also Au⁺ + e⁻) (read 10.10.2026)
- NIST CODATA: Faraday constant F = 96 485.332 12… C/mol, exact (read 10.10.2026)
- CIAAW (IUPAC), Abridged Standard Atomic Weights 2024: Ag 107.87, Cu 63.546, Zn 65.38, Ni 58.693, Cr 51.996, Al 26.982, Au 196.97 (read 10.10.2026)
As of: · Editorial policy
Related tools
- Molar Mass CalculatorCalculate molar mass in g/mol from any chemical formula – with brackets, hydrates like CuSO4·5H2O, mass percent by element, working steps and n = m/M.
- Nernst equation calculatorNernst equation calculator: cell potential at any concentration from standard potential, electron number, temperature and reaction quotient, with ΔG and steps.
- Grams to Moles CalculatorGrams to moles calculator (and back) using molar mass: amount n = m / M, plus the number of particles via the Avogadro constant, with the steps and an example.
- Interactive Periodic Table of the ElementsPeriodic table with all 118 elements: atomic mass, electron configuration, melting and boiling point. Search, temperature slider, colour modes, print to PDF.
- Ohms Law Calculator: Voltage, Current, Resistance and PowerOhms law calculator (Ohm’s law): enter any two of voltage, current, resistance or power and get the other two – with formula wheel and steps.
- Online CalculatorCalculator online, free and instant: type or tap and see the answer as you go – order of operations, brackets, percent, square root, steps and a history list.
- Block and tackle calculator: pulling force and rope lengthBlock and tackle calculator: load, number of supporting rope segments and efficiency give the pulling force in N and kg and the length of rope you have to pull.
- Synchronous speed calculator: motor rpm, slip and loadSynchronous speed calculator for AC motors: 120 × frequency ÷ poles, slip in rpm and percent from the measured speed, and load estimate by the DOE slip method.
- Degree classification calculator (UK)Degree classification calculator for UK honours degrees: enter your year averages and their weighting to see your class and the final-year mark you need.