Expt 048 Micro-Electrolysis of Copper Chloride

U6 Micro-Electrolysis of Copper Chloride

Chemical Concepts

 A battery is like an electron pump, and conducting wires are similar to pipes, allowing electrons to flow from one site to another.  When applied to a chemical solution (electrolysis), a battery can pump electrons away from a reactant at one electrode (The reactant that is losing electrons, is said to be "oxidized"; the electrode, where this occurs, is known as the "anode.").  The battery can simultaneously pump electrons onto another reactant at the other electrode (The reactant that is gaining electrons, is said to be "reduced"; the electrode, where this occurs, is known as the "cathode.").  A chemical reaction consumes the reactants.

Objective : to determine the charge of products formed when an electric current is passed through a

copper (II) chloride (CuCl2) solution.

Prelab questions: Answer in complete sentences in your lab NB.

1. Observe and record the conductivity of the solid CuCl2 and the CuCl2 solution. 2. Based on our discussion of the results of the Conductivity Lab, what does this suggest about this substance as a solid and in solution? What kind of substance is copper chloride?

3. Describe and sketch happens to the CuCl2 particles when they dissolve in water.

Procedure

1. Obtain a micro U-tube filled with copper(II) chloride (CuCl2) solution and a 9-V battery with micro carbon (graphite) rods. (Be careful, the rods break easily!) Record the color of the copper chloride solution.

2. Place the U-tube in a small beaker, then place the electrodes in the CuCl2 solution -- one at each end of the U-tube. Each rod should be about half submerged in the solution. Do not submerge them all the way up to their connecting wires. Observe the reactions taking place at each electrode (rod). Also carefully sniff each electrode. Record.

3. Sketch the U-tube apparatus right after you set it up and after you allow the reaction to run for approximately 30 minutes. Label your sketch:  positive (+) electrode (connected to the red wire)  negative (-) electrode (connected to the black wire). Record what you observe happening at each electrode. Record any changes in the color of the solution in the u-tube.

4. Label your beaker and place it in the fume hood.

5. Observe, sketch and label what has occurred after 24 hours. 6. Conclusions: Answer the following in complete sentences in your lab NB. a. describe the changes that occurred at each of the two electrodes. b. label each electrode with the product observed; explain what you think has happened to produce what you see. c. label the positive and negative electrodes; d. indicate where electrons are being lost by particles and where electrons are being gained by particles; e. label the "cathode" and the "anode"; f. indicate the direction that the electrons are flowing through the wires. g. based on your observations above, assign a charge to the ions in copper chloride.