Explain the electrolysis of molten lead(II) bromide, including the role of heating, electron flow, anode/cathode labeling, and half-ionic equations.

Here are the answers to your questions:

10.

a) Explain why heating is necessary in this experiment.
Heating is necessary to melt the solid lead(II) bromide. In the solid state, the ions are held in fixed positions and cannot move to conduct electricity. When molten, the ions become mobile and are free to move, allowing the substance to conduct electricity.

b) Indicate on the diagram:

i) The flow of electrons.
Electrons flow from the negative terminal of the battery, through the switch and bulb, to the cathode. They are released at the anode and flow back to the positive terminal of the battery. (This would be indicated by arrows on the wires in the diagram, pointing from the negative terminal towards the cathode, and from the anode towards the positive terminal).

ii) Label the anode and cathode.
The electrode connected to the positive terminal of the battery is the anode.
The electrode connected to the negative terminal of the battery is the cathode.
(These labels would be written next to the respective carbon electrodes in the diagram).

c) Write half ionic equations for the reactions taking place at:

i) Anode
At the anode, bromide ions are oxidized:

$$\boxed{2\text{Br}^{-}\text{(l)} \rightarrow \text{Br}_2\text{(g)} + 2\text{e}^{-}}$$

ii) Cathode
At the cathode, lead(II) ions are reduced:

$$\boxed{\text{Pb}^{2+}\text{(l)} + 2\text{e}^{-} \rightarrow \text{Pb(l)}}$$

11. A lighter, Bunsen burner and a wooden splint. Describe an experiment to show that almost colourless zone is made of unburnt gases.
Light the Bunsen burner to produce a non-luminous flame. Carefully insert a wooden splint horizontally into the inner, almost colorless cone of the flame for about 2-3 seconds. Quickly remove the splint. The part of the splint that was in the outer, hot zone will be charred or burnt, while the part that was in the inner, colorless zone will remain unburnt. This shows that the inner cone consists of unburnt gases that are not hot enough to cause combustion of the splint.