Question

Calculate the number of coulombs required to deposit 20.25 g of aluminium (at. mass = 27) from a solution containing Al⁺³.

Answer 1

Given:

Mass of Al deposited (m) = 20.25 gm

Atomic mass of Al = 27 g/mol

Valency of Al = 3 (from Al³⁺)

Faraday’s constant (F) = 96500 C/mol e⁻

Calculations:

Equivalent mass of Al = `27/3`

= 9

Number of gram equivalents = `20.25/9`

= 2.25

Charge required (Q) = No. of equivalents × F

= 2.25 × 96500

= 217125 C​