Question

How much electricity in terms of faraday is required to produce 2 moles of aluminium metal from molten alumina?

Answer 1

The balance reaction will

The charge on Ca in CaCl2

Ca + 2Cl ���� = 0

Cl has �1 charge so that

Ca� + 2(�1) = 0

Ca� ������������ = 2

We have to get 2o g Ca from Ca2+

Number of required moles� = mass / molar mass

Molar mass of Ca is 40 g/mol and required mass of Ca is 20 g

Hence number of moles� �������� = 20/40 ���� = 0.5 mol

Electricity required to produce 1 mol of calcium = 2 F

The electricity required to produce 0.5 mol of calcium

= 0.5 � 2 F

�� = 1 F

(ii)

Charge on Al in Al2O3

2Al� + 3O = 0

Oxygen has �2

2Al +3(�2) � = 0

Al ������� = 3

Change transfer� n = 3

Charge required for 1 mol of Al ���= 3F

Number of moles of Al� = 40 /27� = 1.48

The electricity required to produce 1.48 mol of Al = 1.48� � 3 F

= 4.44 F