An electrolytic cell can be used to plate gold onto other metal surfaces. The plating reaction is: Au (aq) e- --> Au(s) Notice from the reaction that 1 mol e- plates out 1 mol Au(s). Use this stoichiometric relationship to determine how much time is required with an electrical current of 0.200 amp to plate out 0.400 g Au. The amp is a unit of electrical current equivalent to 1 C / s. (Hint: Recall that the charge of an electron is 1.60 x 10-19 C.)

Explanation:

Faraday’s constant can be used to convert the charge (Q) into moles of electrons (n). The charge is the current (I) multiplied by the time

Q = I × t = n × F

Where

Q is charge

I is current = 0.2A

t is time = ?

n is number of mole

F is Faraday constant = 96500C/s

Mass of Au = 0.4 g = 0.0004kg

Molar mass of Au = 197 g/mol

Malar mass = mass / mole

n = 0.4 / 197

n = 2.03× 10^-3 mol

n = 0.00203 mol

t = n × F / I

t = 0.00203 × 96500 / 0.2

t = 979.7 seconds

t = 16.32 minutes.

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