All calculatorsFaraday’s Law Calculator
Compute mass deposited, total charge, time, or current for an electrolysis process using Faraday’s law. Great for fast, step-by-step electrochemistry homework checks.
Background
Faraday’s law relates the amount of substance transformed at an electrode to the total charge passed: m = (Q · M) / (n · F), where m is mass (g), Q charge (C), M molar mass (g·mol−1), n electrons per ion, and F is Faraday’s constant (~96485 C·mol−1).
How it works
Use Q = I · t to get charge (C). Then apply m = (Q · M) / (n · F) to find mass (g) deposited. Rearranging gives formulas for solving for Q, t, or I.
- Solve for m: need M, n, and either Q or (I & t).
- Solve for Q: need m, M, n.
- Solve for t: need m, M, n, and I.
- Solve for I: need m, M, n, and t.
Example Problems & Step-by-Step Solutions
Example 1 (mass from current & time)
Plate Cu from Cu²⁺ (n = 2) using I = 2.50 A for t = 30.0 min (1800 s). M = 63.546 g/mol, F = 96485 C/mol.
- Compute charge: Q = I · t = 2.50 × 1800 = 4500 C.
- Mass: m = (Q · M) / (n · F) = (4500 × 63.546) / (2 × 96485) ≈ 1.48 g.
Example 2 (time from desired mass)
Deposit 0.500 g Ag from Ag⁺ (n = 1) at I = 0.750 A. M = 107.8682 g/mol, F = 96485 C/mol.
- Q = (m · n · F) / M = (0.500 × 1 × 96485) / 107.8682 ≈ 447.1 C.
- t = Q / I = 447.1 / 0.750 ≈ 596 s ≈ 9.93 min.
Frequently Asked Questions
Q: Where do the n values come from?
From the ion charge: Ag⁺ → n = 1, Cu²⁺ → n = 2, Al³⁺ → n = 3, etc.
Q: Does molar mass depend on the ion?
Use the element’s molar mass for the deposited species (e.g., Cu(s) from Cu²⁺ uses 63.546 g/mol).
Q: Which Faraday constant should I use?
Most courses use 96485 C/mol. We default to 96485.33212 C/mol (CODATA style); you can adjust it.
