Transcript Chromium Electroplating Sample Problem

Chromium Electroplating
• Anode mass
decreases:
Cr (s)  Cr 3+ (aq) + 3 e-
• Cathode mass
increases
Cr3+ (aq) + 3 e-  Cr (s)
Eo = - 0.74 v
• Cr plates on the inert
cathode electrode.
• Electroplating is
important in
protecting objects
from corrosion
Electrolytic Cell:
Nonspontaneous— a power source forces
the flow of electrons
What voltage is needed?
Quantifying Electroplating
• Calculate the mass of Chromium metal that will be
electroplated if a current of 0.75 A is run for 5.0 minutes.
Information Needed to Solve the Problem:
•
•
1 ampere (A) = 1 Coulomb per sec
1A=1C/s
The charge of 1 mol of electrons is 96,500 C = 1 Faraday
96,500 C / 1 mol e-
• Cr3+ aq) + 3e-  Cr (s).
•
•
3 mol of electrons will plate 1 mol of Cr
Molar Mass of Cr: 52.0 g/mol
(Answer: 0.040 g Cr)