Question

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.

Answer 1

(i) According to the question,
CA2+ + 2e-1 $\rightarrow$ Ca
40 g
Electricity required to produce 40 g of calcium = 2 F
Therefore, electricity required to produce 20 g of calcium =$\frac{2 \times 20}{4}$ F
= 1 F

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(ii) According to the question,
Al3+ + 3e- $\rightarrow$ Al
27 g
Electricity required to produce 27 g of Al = 3 F
Therefore, electricity required to produce 40 g of Al = $\frac{3 \times 40}{27}$ F
= 4.44 F