Microscale chemistry with a coin and a can
Mahmoud K. El-Marsafy, Peter Schwarz

4. Forced electron transfer from Cl- to Cu2+ ions during electrolysis

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Photos 4.1 - 4.3
 Electrolysis of a mixture of copper salt solution and table salt (1 + 2), testing for chlorine (3)

The solution from experiment 1 is rinsed into a blister by adding drops of concentrated table salt solution.
1 Two pencil leads –connected with a 9-Volt battery- dip into this solution. 2  A layer with the colour of  copper appears on the negative (left) electrode, gas bubbles are around the positive electrode.  3 4 shows the result of testing for chlorine: A white tissue paper wetted by a colourless potassium iodide solution turns brown because iodide was oxidised to iodine by chlorine.
          Reduction:                Cu2+(aq) + 2e- --> Cu(s)
          Oxidation:                          2 Cl-(aq)   --> Cl2 (g)   + 2e-
     Redox reaction:   Cu2+(aq) +   2 Cl-(aq)  --> Cu(s)  + Cl2 (g)

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