Complete the diagram for electrical conduction in lead (II) iodide and explain observations and equations.

Here are the answers to your questions:

7. The diagram below shows an experiment for investigating electrical conduction in lead (II) iodide. Study it and answer the questions that follow:

   • iii) Complete the diagram by indicating the condition missing in the diagram but must be present for electrical conduction to take place. (1mk) The missing condition is heat. A Bunsen burner flame should be drawn under the boiling tube to melt the lead(II) iodide.

   • b) Why is it necessary to leave a gap between the cork and the boiling tube? (1mk) To allow for the escape of any fumes produced (e.g., iodine vapor) and to prevent pressure build-up inside the boiling tube as the contents are heated.

   • c) State two observations that are expected at the end of the experiment. (2mks)

     • i) The bulb will light up, indicating electrical conduction.
     • ii) A grey/silvery solid (lead metal) will be deposited at the cathode.
     • iii) Brown/purple fumes (iodine vapor) will be produced at the anode.

   • d) Write the equation taking place at:

     • Anode: $$2\text{I}^{-}(\text{l}) \longrightarrow \text{I}_{2}(\text{g}) + 2\text{e}^{-}$$
     • Cathode: $$\text{Pb}^{2+}(\text{l}) + 2\text{e}^{-} \longrightarrow \text{Pb}(\text{s})$$

   • e) Why should this experiment be carried out in a fume chamber? (1mk) Because iodine vapor produced at the anode is toxic and corrosive.

   • f) State two applications of electrolysis. (2mks)

     • i) Purification of metals (e.g., copper).
     • ii) Extraction of reactive metals from their ores (e.g., aluminium, sodium).
     • (Other valid answers include electroplating, anodizing, manufacture of chemicals like chlorine and sodium hydroxide).

8. (The image shows a partially drawn structure of 2-methylhexane. Here is the complete structural formula with all hydrogen atoms shown.)

       H   H   H   H   H   H
       |   |   |   |   |   |
   H - C - C - C - C - C - C - H
       |   |   |   |   |   |
       H   C   H   H   H   H
           |
           H
           |
           H
   

   Copy

   This represents 2-methylhexane.