Question

2.644 g of metal (M) was deposited when 8040 coulombs of electricity was passed through molten MF\(_2\) salt. What is the atomic mass of M? (F = 96500 C mol\(^{-1}\))

• A. 63.47 u
• B. 65.54 u
• C. 31.74 u
• D. 61.48 u

Hint:

When calculating atomic masses using electrolysis data, always keep in mind the valency of the ion (z), as it plays a critical role in determining the atomic mass.

Answer 1

The Correct Option is A

We can use Faraday’s law of electrolysis to calculate the atomic mass. The formula is: \[ m = \frac{M \cdot Q}{F \cdot z} \] Where: - \(m = 2.644 \, \text{g}\),
- \(Q = 8040 \, \text{C}\),
- \(F = 96500 \, \text{C mol}^{-1}\), - \(z = 2\) (since M is divalent). Rearranging the formula: \[ M = \frac{m \cdot F \cdot z}{Q} = \frac{2.644 \times 96500 \times 2}{8040} = 63.47 \, \text{u} \] Thus, the atomic mass of M is 63.47 u.