# What mass of gold is produced when 24.9 A of current are passed through a gold solution for 25.0 min ?

Metal plating is done by passing current through a metal solution. For example, an item can become gold plated by attaching the item to a power source and submerging it into a Au3+ solution. The item itself serves as the cathode, at which the Au3+ ions are reduced to Au(s). A piece of solid gold is used as the anode and is also connected to the power source, thus completing the circuit.

What mass of gold is produced when 24.9 A of current are passed through a gold solution for 25.0 min ?

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• This part:

(24.9 A) × (25.0 × 60 s) = 37350 C

I will rewrite with some unit changes:

(24.9 C/s) × (25.0 mim × 60 s/min) = 37350 C

One ampere equals one Coulomb per second is an important identity to remember in problems of this type.

• Au³⁺(aq) + 3e⁻ → Au(s)

Quantity of electricity, Q = It = (24.9 A) × (25.0 × 60 s) = 37350 C

1 mole of e⁻ carries 96500 C of electricity.

No. of moles of electrons = (37350 C) / (96500 C/mol) = 0.387 mol

According to the equation, mole ratio e⁻ : Au = 3 : 1

No. of moles Au produced = (0.387 mol) × (1/3) = 0.129 mol

Molar mass of Au = 197.0 g/mol

Mass of Au produced = (197.0 g/mol) × (0.129 mol) = 25.4 g