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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry 4th edition

Problem 18.81

How many coulombs of electric charge are required to deposit 25.0 g of Cu(s) at the cathode in the electrolysis of CuSO4(aq)?






Answer:

25.0 g Cu(s) = 25.0/63.5 g/mol = 0.394 mol

Cu2+(aq) + 2 eCu(s)

so 0.394 mol Cu requires 2×0.394 = 0.788 mol electrons

coulombs = mols electrons × Faraday's constant = 0.788 × 96485 = 76000 coulombs.