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Electrolysis and Faraday's law

In a galvanic cell, a spontaneous redox reaction produces electric current, as in a battery. In electrolysis it goes the other way: electric current drives a non-spontaneous redox reaction. Faraday's law relates the mass deposited at an electrode to the current, time, and number of electrons transferred per ion.

m = \frac{I\,t\,M}{z\,F}

mass deposited during electrolysis

Symbols

$I$	current	A
$t$	time	s
$M$	molar mass of the substance	g/mol
$z$	number of electrons transferred per ion
$F$	Faraday's constant, $96.485$ C/mol

Example

10 A for 10 min ( $t=600$ s) on Ag+ ( $M = 107.87$ , $z=1$ ):

$m = \dfrac{10\cdot 600\cdot 107.87}{1\cdot 96.485} \approx 6.71$ g.

Remember to convert time to seconds — Faraday's constant is defined per second via amperes.

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Part of General Chemistry: Thermochemistry and electrochemistry.