Lab Exercise #1: Quantitative Electrolysis

Experimental Design: A steel can is placed in an electroplating cell and connected as the cathode. An electric current of 3.46 A flows through the cell, which contains a 3.25 mol/L solution of tin(II) chloride for 6.00 minutes.

Questions: 1. What mass of tin should be plated at the cathode during this reaction? 2. Prior to being electroplated with tin, the steel can had a mass of 117.34 g. After 6.00 minutes of electroplating, the can has a mass of 118.05 g. Calculate the percent error associated with this process.

Lab Exercise #2: Using Quantitative Electrolysis to Determine an Oxidation State

Experimental Design: A solution containing vanadium ions with an unknown oxidation state is electrolyzed with a current of 1.50 A for 30.0 minutes. At the completion of this electrolytic process, a mass of 0.475 g of vanadium metal has been plated onto the cathode.

Question: 1. What is the oxidation state of the vanadium ions in the solution? Chem 30 Electrolytic Cells

1. The electroplating of nickel onto a silver-coated master disc is a step in the manufacturing of CDs.

a. When nickel is plated onto the silver master disc, is the master disc the anode or the cathode of the cell? Explain.

b. Calculate the amount of charge needed (in C) to plate each gram of nickel onto the master disc. Assume that the plating process involves the reduction of nickel(II) ions. (q = 3.29 x 103 C)

2. Most industrial reactions take place on a much larger scale than the reactions in a laboratory or classroom. The voltage used in a Downs cell for the industrial electrolysis of molten sodium chloride is not very high, about 7V to 8V. However, the current used is 25000 A to 40000 A. Assuming a current of 3.0 x 104A, determine the mass of sodium and the mass of chlorine made in 24 h in one Downs cell. Express each mass in kg. 2 2 (msodium = 6.2 x 10 kg; mchlorine = 9.5 x 10 kg)

3. Canada is a major producer of aluminium by the electrolysis of bauxite. However, there are no bauxite mines in Canada, and all the ore must be imported. Explain why aluminium is produced in Canada.

4. How long (in h) would it take a 50.0 kA current to produce 1.00 t of aluminum from molten aluminum oxide? (t = 59.6 h)

5. In an electrolysis experiment, a student passed 1.57 A of current through an aqueous solution of lead (II) nitrate containing a 7.63 g piece of lead foil as the cathode. What is the final mass of the lead electrode after 17.0 min? (mf = 9.35 g)

6. A trophy company is setting up a nickel-plating cell using an electrolyte of nickel(II) nitrate. Predict the current required to produce nickel metal at a rate of 5.00 g/min. (I = 274 A)