Question

How much time (in hours) is required to plate out 25.0 g of gold metal from a solution of Au(NO3)3 when the current is 2.00 amperes and the electrode efficiency is only 65%?

Answer 1

Given Info : 25 g of gold metal from a solution of Au(NO3)3 when the current is 2.00 Ampere and the electrode efficiency is only 65 %.

To find : Time required to plate out 25 g of gold metal is..

solution : here, Au³⁺ + 3e¯ => Au

here you see, to deposit one mole of Aurum (gold), 3 moles of electrons are required.

mass of Au = 25g

atomic mass of Au = 197 g/mol

so, no of moles of Au = 25/197 = 0.127 mol

so no of moles of electrons = 3 × 0.127 mol

now no of moles electrons = charge/Faraday's constant

we know, Faraday's constant is 96500C

⇒3 × 0.127 × 96500 C = charge

current, I = 2 A

efficiency, η = 65 % = 0.65

so, charge = ηIt = 3 × × 0.127 × 96500 C

⇒0.65 × 2 × t = 36,766.5 C

⇒t = 36,766.5/1.3 = 28,281.9231 sec = 7.856 hrs

Therefore the required time is 7.856 hrs.