Question

The number of Faradays(F) required to produce 20g of calcium from molten $CaCl_2$ (Atomic mass of $CaCl_2$ g $mol^{-1}$) is :

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The Correct Option is A

To determine the number of Faradays required to produce 20 g of calcium from molten \(CaCl_2\), we need to follow these steps:

1. First, understand that producing calcium from molten \(CaCl_2\) is an electrolytic process. In electrolysis, the amount of element deposited is governed by Faraday's laws of electrolysis.
2. The reaction at the cathode for the electrolysis of \(CaCl_2\) is: \(Ca^{2+} + 2e^- \rightarrow Ca\)
3. This means that two moles of electrons, or 2 Faradays, are required to produce one mole of calcium.
4. Next, calculate the number of moles of calcium in 20 grams.
5. Given, the atomic mass of calcium \(Ca = 40 \, g/mol\).
6. Calculate moles of calcium: \(\text{Moles of calcium} = \frac{\text{Mass of calcium (g)}}{\text{Molar mass of calcium (g/mol)}} = \frac{20}{40} = 0.5 \, moles\)
7. Since 2 Faradays are needed to produce one mole of calcium, then for 0.5 moles of calcium, we will need: \(2 \times 0.5 = 1 \, \text{Faraday}\)

Therefore, the number of Faradays required to produce 20 g of calcium is 1. Thus, option 1 is correct.