re: HSC Chemistry Marathon Archive
4/4. Though precipitation by iodide ions may be preferred for (a) because AAS is more suitable when you know there is definitely lead present and you want to know how much lead there is.
____________________________________________
NEXT QUESTION:
a) Construct a flow chart showing how polystyrene can be produced from petroleum. (3)
b) In your study of chemistry, you had to research about a recently developed biopolymer.
Describe how this polymer can be synthesised and relate uses of this biopolymer to its properties. (5)
a) Fractional Distillation of Petroleum ---> Catalytic and Thermal Cracking of higher chained hydrocarbons to obtain ethylene (as not enough is 'produced' from fractional distillation) ----> Substition reaction of ethylene with Benzene??? (i don't have a clue how the benzene ring is swapped for a hydrogen in ethylene) ----> This produces styrene ----> Styrene monomers are joined together in an addition reaction involving steps of initiation, propagation, termination -----> This produces polystyrene.
A biopolymer which can be synthesised is PHB. It is produced by feeding bacteria such as Alcigenes Eutrophus or E.Coli on a nurient rich diet until large colonies of the bacteria begin to form, and at this point, glucose is added and the nutrients such as nitrates removed from the diet. This unnatural high energy, low nutrient diet, makes the bacteria automatically secrete PHB as an energy store (similar to fat of humans). PHB is naturally occuring which means it is non toxic and renewable. It is also biodegrable as it decomposes into CO2 and H20, reducing landfill. PHB is also biocompatible hence can be used in medical sutures that don't need removal and decompose over time, hence removing the need or follow up appointments. Finally, it has physical properties similar to propylene meaning it can be used readily as a substiture for polypropylene.
