(a) Name one gaseous hydrocarbon which is

(i) used for welding.

(ii) a major raw material for the plastic industry.

(b) Write the structural formula of the hydrocarbon in (a)(i) above. Name the process by which it can be converted to neoprene rubber.

(c) Potatoes contain a high proportion of carbohydrate.

(i) Give the main product formed when potatoes are dehydrated completely

(ii) Describe how you would convert potatoes to ethanol. State the reactions involved the process and write equation for the final stage of the conversion.

(iii) Draw a labelled diagram of the apparatus you  would use to obtain a sample of fairly pure ethanol from the product formed in (c)(ii) above. What is the name given to the technique?