An aluminium smelter uses electricity to reduce aluminium from Al_2 O_3 of pure

Question

An aluminium smelter uses electricity to reduce aluminium from Al_2 O_3 of pure aluminium. The molar mass of aluminium is 26.98 g/mol Avagadro's number is 6.022 times 10^22/mol Each molecule of Aluminium requires 3 electrons to bring it from A1^3 to Al There are 6.24 times 10 electrons in 1 Coulomb of negative charge a) How many Coulombs are required to generate 1 g of pure Aluminium? b) An ammeter at a smelter records the current entering an electrode in the reducing chamber every 5 minutes: c) Estimate the total amount of aluminium produced at that electrode over the I hour period. d) If the electrode at 4 V. what power is required at time 0?

Explanation / Answer

Answer:- a) 1 g of aluminium implies number of moles of aluminium is 1 / 26.98 = 0.037. But one mole is equal to one Avogadro number molecules i.e 6.022 x 1022 . Hence for 0.037 mol, number of Al molecules is equal to 0.037 x 6.022 x 1022 = 2.23 x 1021 molecules.

Now for one molecule Al we need three electronic charge, hence for 2.23 x 1021 molecules we need 3 x 2.23 x 1021 electrons = 6.69 x 1021 electrons. So in terms of Coulomb we can write (6.69 x 1021 ) / (6.24 x 1018 ) = 1063.59 Coulomb.

b) To calculate total aluminium produced we need to calculate total amount of charge passed to the electrode in one hour. In an average we can write total charge passed is equal to-

Q = (4 +3.5 + 3.1 + 2.7 + 2.4 + 2.1 + 1.9 + 1.7 + 1.5 + 1.4 + 1.3 + 1.2) x103 x (5 x 60 )

   = 8040 x 103 Coulomb

As calculated above, 1063.59 Coulomb gives one gram of Al, so 8040000 Coulomb will give,           8040000 / 1063.59 gram of aluminium, i.e 7559.3 gram or 7.5593 kg of aluminium.

c) As supply voltage is 4 V and at t = 0 m the current is 4 kA i.e 4000A. Hence power required at t = 0 is - 4 x 4000 watt which gives power equal to 16 kW.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.