Question

How many Coulombs of charge are needed to create 19.7 g of Au(s) from Au3+(aq)? 1. 289, 456 C 2. 28, 945 C 3. 0.1 C 4. 0.3 C 5. 96, 485 C 6. 9, 649 C

Answer 1

We are given,

Au³⁺ +3e- → Au

In the reduction of Au3+ to Au, 3 moles of electrons is needed.

Also,

No. of moles of Au given = Mass of Au given / Molar mass of Au

Mass of Au given = 19.7 g

Molar mass of Au = 197 g/mol

No. of moles of Au given = (19.7 g) / (197 g/mol) = 0.1 mol

Thus, no. of mole electrons of Au given = (3 moles of electrons) * (No. of moles of Au)

No. of mole electrons of Au given = (3 * 0.1) = 0.3 mole electrons of Au

Faraday Constant (F) represents the amount of charge carried by 1 mole electrons

Faraday Constant (F) = 96485 C / mol

Thus,

Charge contained by 1 mole electrons of Au = 96485 C

So,

Charge contained by 0.3 mole electrons of Au = (0.3) * (96485 C) = 28945 C