Using Faraday in electrochemical calculations. As we saw earlier, the mass of metal deposited in an elecroplating cell is directly proportional to the number of electrons pumped through the circuit. The number of electrons are represented by charge. Charge is measured in units called coulombs(Q). Charge = current(amps) X time(seconds) Q = I X t It is found that "One mole of electrons produce 96,500 coulomb of charge". The charge on one mole of electrons is called a faraday. 1 faraday = 96,500 coulomb / mol. We can now calculate the charge on any given number of mole of electrons. eg. 3 mole of electrons will have a charge of (3 X 96,500) =289,500C How can we use this information? Example . A silver plating cell operates for 15 minutes at a current of 20.0A. What mass of silver is deposited at the cathode? Step 1 Calculate the charge passed through the cell during the 15 minute period. Q = I X t Q = 20.0 X (15 X 60)s = 18,000C (time must be expressed in seconds) Step 2 Calculate the mole of electrons passed through the circuit. mole = 18,000C/96,500C/mol = 0.187 mole. Step 3 Calculate the mass of silver Ag+(aq) + e => Ag(s) According to the equation above 0.187 mole of electrons will produce 0.187 mole of silver. The mass of silver is therefore 0.187 X 107.9 = 20.13grams.