Question

What mass of Cr(s) (in g) may be electrodeposited from application of a 0.436 A current to a solution of Cr3+(aq) over 3.57 min?

Answer 1

The electrochemical reation at the cathode will be:

Cr(3+) + 3e(-) = Cr

this means, chromium ions in solution will deposit out as chromium metal on the cathode when three electrons per chromium ion are passed into solution.

Using Faraday's equation; W= (I*t*A)/n*F

where,

• W = weight of electrodeposited metal in grams.
• I = current in coulombs per second.
• t = time in seconds.
• A = atomic weight of the metal in grams per mole.
• n = valence of the dissolved metal in solution in equivalents per mole.
• F = Faraday's constant in coulombs per equivalent. F = 96,485.309 coulombs/equivalent.

W= (0.436*(3.57*60)*54.94)/(3*96485.309) = 0.017726 grams.