How much electricity in terms of Faraday is required to produce (i) 20.0 g of Ca from molten CaCl2? (ii) 40.0 g of Al from molten Al2O3?
(1) Ca2++2e−→Ca 1 mole (40 g) of Ca will require 2 F of electricity. 20 g (0.5 mole) of Ca will require 1 F of electricity. (2) Al3++3e−→Al 1 mole (27 g) of Al will require 3 moles of electrons. 40 g of Al will require 273×40F=4.4 F
