how to use faradays law in the question?

Question

A student wants to plate a clasp on a school lanyard with nickel.

a) Suggest a substance that the student could use as an anode. (include rationale)

b)The student wants to plate 5.0 g of nickel using a nickel sulfate solution, but has only 10 min to do so. What current is required to achieve this?

Answer 1

Yes, in this question, since you do know the time, and need to solve for current, you would use Faraday's law.

(a) Since you want to deposit Ni(s) from a solution of Ni2+(aq), this means the Ni2+ must be reduced, which takes place at the cathode (the clasp). Thus, the anode must have a greater reduction potential than the material that the clasp is made of. Usually, Ni would be the electrode and electroplating is done using an electrolytic cell, not a galvanic cell, but one can use any metal as the anode as long as it has a greater reduction potential.

 

(b) Ni²⁺ + 2e- ==> Ni(s)

5.0 g Ni x 1 mole Ni/58.7 g = 0.0852 moles Ni

0.0852 moles Ni x 2e-/mole = .1704 moles electrons

0.1704 moles e- x 96,500 coulombs/mole e- = 16,444 coulombs

10 minutes = 10 min x 60 sec/min = 600 seconds

From amp = C/sec you have amps = 16,400 C/600 sec = 27.3 amps = current needed