Moles of Cl 2 produced to moles of electrons required Liters of Cl 2 produced to moles of Cl 2 produced If 4.73 L of Cl 2 (at STP) is produced at the anode, what is the current in amperes?ġ) The entire calculation done dimensional analysis style: (96485 C/mol) (0.02769438 mol) = 2672.1 C of charge passedĢ672.1 C / 2880 s = 0.928 A (to three sig figs)Įxample #11: A constant current is passed through an electrolytic cell containing molten MgCl 2 for 17.0 h. Three moles of electrons are required for every one mole of Cr deposited. What is the oxidation state of the vanadium product? Its mass decreases by 114 mg during the passage of 650. The charge of one electron is 1.602 x 10¯ 19 coulombĮach copper ion needs two electrons to become copper. Round to three sig figs for a final answer of 6.00 gĮxample #8: Using a current of 4.75 A, how many minutes does it take to plate out 1.50 g of Cu from a CuSO 4 solution? Two moles of electrons per one mole of Mg depositedĠ.493407 mol / 2 = 0.2467035 mol of Mg deposited What mass of Mg is produced?Ĥ7606.4 C / 96485 C/mol = 0.493407 mol of electrons (0.000389364 mol) (96485 C/mol) = 37.56778 Cĥ) Determine time required to transfer charge:Įxample #7: A constant current of 0.912 A is passed through an electrolytic cell containing molten MgCl 2 for 14.5 h. What is the current? What is the half reaction for the deposition of silver?Ġ.3650 g divided by 107.8682 g/mol = 0.00338376 molĠ.000389364 mol of Ag + plated out requires 0.000389364 mol of electronsĤ) Determine Coulombs of charge that was transfered: Therefore, every mole of Ni plated out requires two moles of electrons.Ġ.6815076 mol x 2 = 1.363015 mol e¯ requiredġ.363015 mol e¯ x 96,485.309 C/mol = 1.31511 x 10 5 CĤ) Convert to seconds required to deliver the Coulombs determined in step 3 (remember, 1 A = 1 C/sec):ġ.31511 x 10 5 C divided by 3.450 C/sec = 3.8119 x 10 4 secģ.8119 x 10 4 sec divided by 60 sec/min = 635.3 minĮxample #3: What is the equivalent weight of a metal if a current of 0.2500 amp causes 0.5240 g of metal to plate out a solution undergoing electrolysis in 1 hour? (Comment: One mole of electrons will plate out one equivalent weight of metal.)ġ) Determine total Coulombs of charge delivered:Ģ) Determine moles of electrons in 900.0 C:ĩ00.0 C divided by 96,485.309 C/mol of electrons = 9.327845 x 10¯ 3 mol of electronsģ) Determine mass of metal plated out by one mole of electrons:Ġ.5240 g / 9.327845 x 10¯ 3 mol = 56.18 g per equivalent weightĮxample #4: How many hours will it take to plate out copper in 200.0 mL of a 0.0 M Cu 2+ solution using a current of 0.200 amp?ġ) Determine moles of copper to be plated out:Ġ.03000 mol x 2 = 0.06000 mol e¯ requiredĠ.06000 mol e¯ x 96,485.309 C/mol = 5789.12 Cĥ789.12 C divided by 0.200 C/sec = 28945.6 secĢ8945.6 sec divided by 3600 sec/hr = 8.04 hoursĮxample #5: A constant electric current deposits 0.3650 g of silver metal in 12960 seconds from a solution of silver nitrate. Therefore, every mole of Cu plated out requires two moles of electrons.ġ.573663 mol x 2 = 3.147326 mol e¯ requiredģ) Convert moles of electrons to Coulombs of charge:ģ.147326 mol e¯ x 96,485.309 C/mol = 3.0367 x 10 5 CĮxample #2: How many minutes will take to plate out 40.00 g of Ni form a solution of NiSO 4 using a current of 3.450 amp?Ĥ0.00 g divided by 58.6934 g/mole = 0.6815076 mol General note: I kept all the digits on my calculator I rounded off to the final answer at the end of each problem.Įxample #1: Calculate the quantity of electricity (Coulombs) necessary to deposit 100.00 g of copper from a CuSO 4 solution.ġ00.00 g divided by 63.546 g/mole = 1.573663 molĢ) Determine moles of electrons required:
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