Chemistry / Unit 11 Chem 2231 worked example, 60 to 90 seconds
Calculating Product Quantity from Current and Time
The idea
Calculating the quantity of product formed by electrolysis means converting current and time into total charge in coulombs, dividing by Faraday's constant to find moles of electrons, then using the half-reaction's electron stoichiometry to convert to moles of product, and finally to mass if needed.
In practice
Passing 5.00 A for 1.00 hour delivers charge = (5.00 A)(3600 s) = 18,000 C. Dividing by Faraday's constant, 96,485 C/mol, gives about 0.187 mol of electrons. For Cu²⁺ + 2 e⁻ → Cu, that two-electron stoichiometry yields 0.0933 mol of copper metal deposited, which converts to roughly 5.93 g using copper's molar mass.
Where people slip
Skipping the conversion from current and time to total charge, and dividing current directly by Faraday's constant, treats amperes as if they were coulombs already, an easy and consequential unit slip.
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