Question 18.PS.12: Using the Faraday Constant How many grams of copper will be ......

Principles of Chemistry The Molecular Science [1096176]

Using the Faraday Constant

How many grams of copper will be deposited at the cathode of an electrolysis cell if an electric current of 15 mA is applied for 1.0 h through an aqueous solution containing excess $Cu^{2+}$ ions?

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0.018 g Cu

Strategy and Explanation We use the strategy presented in Figure 18.19. First, we write and balance the relevant half-reaction that occurs at the cathode.

$Cu^{2+}(aq) + 2 e^- → Cu(s)$

Then, we calculate the quantity of charge transferred.

Charge = 15 × 10^{-3}  A × 3600  s = 15 × 10^{-3}  C/s × 3600. s = 54  C

Finally, we determine the mass of copper deposited.

$(54 C)(\frac{1 mol e^-}{9.65 × 10^4 C})(\frac{1 mol Cu}{2 mol e^-})(\frac{63.5 g Cu}{1 mol Cu}) = 0.018 g Cu$

18.19

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