m = (I × t × M) ÷ (n × F) — fill in every field except the one you want; the empty field is solved for.
Metal:
g/mol
e⁻
Mass deposited (m) = 2.371 g
- Convert t: 60 min =
3,600 s - Rearrange:
m = (I × t × M) ÷ (n × 96485 C/mol) - Substitute:
((2 A) × (3,600 s) × (63.546 g/mol)) ÷ ((2 e⁻) × 96485 C/mol)=2.371 g
How it works
Faraday's first law combines charge (Q = I × t), the Faraday constant (96,485 C per mole of electrons) and the number of electrons per ion: m = (I × t × M) ÷ (n × F). Time is converted to seconds and current to amperes before solving.
This gives the theoretical mass for 100 % current efficiency. Real plating baths lose some current to side reactions such as hydrogen evolution, so industrial calculations often multiply by a current efficiency (for example 0.95 for acid copper baths).
Frequently asked questions
- How do I calculate the mass deposited in electrolysis?
- Multiply current by time to get charge, divide by 96,485 C/mol and by the electrons per ion to get moles of metal, then multiply by the molar mass. 2.0 A for 1 hour deposits (2.0 × 3600 × 63.55) ÷ (2 × 96,485) ≈ 2.37 g of copper.
- What is n?
- The number of electrons needed to deposit one atom: 2 for Cu²⁺ → Cu, 1 for Ag⁺ → Ag, 3 for Al³⁺ → Al.
- What is the Faraday constant?
- The charge on one mole of electrons: 96,485.33 C/mol, the product of the elementary charge and the Avogadro constant.
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