Short Answer 1) If a constant current of 1.50 × 108 A is passed through a molten

Question

Short Answer

1) If a constant current of 1.50 × 108 A is passed through a molten mixture of aluminum oxide and cryolite for 4.00 hour ________ kg of aluminum can be produced.

2) The standard cell potential for the following galvanic cell is 0.71 V.
Pb(s)|Pb2+(aq)||Al3+(aq)|Al
This reaction has an equilibrium constant, K = ________.

3)The standard cell potential for the following galvanic cell is 1.21 V.
Al(s)|Al3+(aq)||Fe2+(aq)|Fe(s)
When [Al3+] = 0.10 M and [Fe2+] = 0.10 M, will the cell potential at 25°C be less than, the same as, or greater than 1.21 V?

Explanation / Answer

Balanced equation:
2 Al2O3 + 3 C ====> 4 Al + 3 CO2

Al3++ 3e- ---> Al

Calculate the number of moles of electrons.

Convert time in seconds

I = 1.50x 108 A * 4 Hr * 3600 s / 1Hr = 2.16 x1012 C

2.16 x1012 C x (1 mol e- /  96485 C) = 2.24 x 107 mole e-

According to the equations, three moles of electrons produce one mole of aluminium.

2.24 x 107 mole e- (1 mol Al / 3 mole e-) = 7.46 x 106 mole Al (26.98 g / mol Al) = 2.01 x 108 g Al = 20100 kg Al

Hence 20100 kg Al can be produced

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