Question

How many grams of copper will be plated out by a current of 2.3 a applied for 35 minutes to a 0.50 m solution of copper (ii) sulfate?

Answer 1

When the magnitude of the charge Q = I*T

when we have I current = 2.3

and T =   35 min * 60 = 2100 s

by substitution:

∴ Q = 2.3 * 2100

       = 4830 C

according to this reaction equation:

Cu2+ + 2e-  → Cu

we can see that 1 mol Cu2+ need 2 mol e- to produce Cu

mol of electron e- = Q / faraday's constant

                          = 4830 / 96485 

                          = 0.05 mol

when 1 mol Cu2+  → 2 mol e-

                 ??          ←  0.05 mol

∴ moles Cu2+ = 0.05 /2 = 0.025 mol

∴ mass Cu2+ = moles Cu2+ * molar mass Cu2+

                       = 0.025 * 64

                      = 1.6 g