electrochemistry Background: During clectrodcposition of cupric ions (Cu11) as c
ID: 931598 • Letter: E
Question
electrochemistryBackground: During clectrodcposition of cupric ions (Cu11) as copper metal (Cu degree ). some of the reduction current is wasted because oxygen from air is being reduced too. To avoid oxygen reduction during electrodeposition of copper, the copper plating solution is often bubbled vigorously (called sparging) with nitrogen to remove oxygen from air. A disk electrode is put 0.5 centimeters below the solution level of a cell; and the oxygen is removed from the solution by pre-sparging with nitrogen. The solution sparging is stopped and the solution is NOT stirred but is open to air at the beginning of copper plating. To one significant figure, how long can you electroplate copper in this pre-sparged solution before oxygen reduction begins to occur in addition to copper reduction? Recall that the linear diffusion law is x^2-Dt where x is the normal path from one plane parallel to another plane. D is the diffusion coefficient and t is the time to travel from on one plane to the other in a straight line. The diffusion coefficient of oxygen in solution is 10^5 cn^2/s.
Explanation / Answer
The time required for electroplating before O2 reduction would be,
c) 7 hours
Using formula given,
x^2 = Dt
t = (0.5 cm)^2/10^-5 cm^2/s = 25000 s = 7 hour
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