Ncert Exercises & Solutions

3.13 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?

Hint: Use faraday's first law of electrolysis

(i) According to the question,

{Ca}^{2 +} + 2 e^{- 1} \to 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}{40} F

= 1 F

(ii) According to the question,

{Al}^{3 +} + 3 e^{-} \to Al

27 g

Electricity required to produce 27 g of Al= 3 F

Therefore, the electricity required to produce 40 g of Al

= \frac{3 \times 40}{27} F

= 4.44 F