Question

What constant current (in amperes) is required to produce aluminum by the Hall-Heroult process at a rate of 40.0 kg/h?

Please answer the following questions:

The rate of aluminum production in grams per second is _________ (3 significant figures)

The number of moles of electrons transferred in the balanced reactions is_______ moles.

The change on a mole of electrons is _______ coulombs. (3 significant figures)

The current required for the process is ________amperes. (3 significant figures)

Answer 1

3 moles of electrons are required to reduce Al³⁺ to aluminum

Al³⁺ + 3e^- ------ Al

This method will produce 9 g of aluminum

rate of aluminium production = 40 Kg/h

number of moles produce in 1 hour = (40x1000)/ 27 = 1418.4 mol

1. aluminium production in g/sec= 11.111 g/sec

2. number of moles in balanced reaction = 1418.4 mol

3. current required:

I = -(n_e/a_Al) x F x(dn_Al/dt) = -( 3/1) x 96.4853 x 40 = 11578.2 amperes

where:  I = current at the electrode (the cathode is this case), F = Faraday`s constant (96,485.3), dn_Al/dt = the production of Al for a given time period , a_Al = 1 and n_e = 3