Faraday's Second Law of Electrolysis
When the same quantity of electricity passes through different electrolytes, the masses deposited are proportional to their chemical equivalent weights.
Formula / equation
m₁/m₂ = E₁/E₂
Unit
g
In depth
An ion needing more electrons per atom yields less mass for the same charge. The law shows that electrolysis counts electrons rather than atoms, and combining both laws gives the amount deposited from the current, time and the number of electrons in the half-equation.
Examples in the real world
One faraday deposits 108 g of silver but only 31.8 g of copper, since Cu²⁺ needs two electrons.