Question

How many grams of cobalt may be formed by the passage of 2.92 amps for 2.95 hours through an electrolytic cell that contains an aqueous cobaltic (Co(III)) salt.

Answer 1

Co³⁺ + 3e^- ---->Co(s)

1 mole Co(s) will form from 3 moles electron

charge transferred for 2.92 A and 2.95 hours

1A = 1C/s

2.95 h = 2.95 x 3600 = 10620s

charge = 10620 s x 2.92 C/s = 31010.4 C

96485 C = 1 mole charge

31010.4 C = 1/96485 x 31010.4 = 0.3214 mol electron

3 mole electron will get 1 mol Co(s)

0.3214 mol electron will give = 1/3 x 0.3214 = 0.1071 mol Co(s)

cobalt molar mass = 58.93 g/mol

0.1071 mol Co(s) = 0.1071 mol x 58.93 g/mol = 6.31339 g ~ 6.31 g