Faraday’s laws of electrolysis

Faraday’s first law: the mass of substance released at an electrode is directly proportional to the quantity of electricity that passed through the electrolyte (Q = I·t). The second law: when the same quantity of electricity passes, the masses of different substances released are proportional to their equivalent masses. Together they give m = E·I·t/F, where F is the Faraday constant, ≈ 96 485 C/mol (96 500 is used in problems), the charge of 1 mole of electrons. The number of equivalents of electricity is n(eq) = I·t/96500; the same number of equivalents of substance is released. For example, 1 equivalent is Ag 108 g, Cu 32 g, Al 9 g, H₂ 1 g (11.2 L under normal conditions), O₂ 8 g (5.6 L), Cl₂ 35.5 g (11.2 L). The time is t = m·96500/(E·I) and the current I = m·96500/(E·t). The unit of F is C/mol; the farad is the unit of capacitance, so do not confuse them. In practice part of the current goes to side reactions, so the real mass may be less than the theoretical one (current efficiency).