IB Docs (2) Team MC test: Polymers
Multiple choice test on A.5 Polymers
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
Which are correct statements about thermosetting polymers?
I. They soften when heated and harden when cooled.
II. Once cured, they cannot be remoulded.
III. They form prepolymers in a soft solid or viscous state.
Only thermoplastics can be remoulded as they soften when heated and harden when cooled.
Which can undergo addition polymerization to produce an atactic polymer?
Atatctic polymers can only be formed when every other carbon atom in the carbon chain contains two different groups attached to it (in addition to other two carbon atoms). In atactic polymers these two groups are orientated in a random fashion.
Which statement is correct about high density poly(ethene)?
The fact that HDPE has little or no branching means the molecules of the polymers can pack more closely together than in LDPE making HDPE more rigid than LDPE.
What collective name is given to small molecules that, when added during the formation of polymers like PVC, alter the physical properties of the polymer such as flexibility?
Plasticizers fit between between the long polymer chains and weaken the attractive forces between the chains making the polymer more flexible.
What is added during the formation of polystyrene to make expanded polystyrene?
A volatile hydrocarbon, such as pentane, is added and then steam passed through. The volatile hydrocarbon escapes leaving pockets of air trapped within the polystyrene.
What name is given to polymers which can be deformed under force but return to almost their original shape when the stress is removed?
The general name is elastomer, butyl rubber is one particular type of elastomer.
Which statement explains why the atom economy for the formation of addition polymers from alkenes or from substituted alkenes is theoretically 100%.
Because the only product is the addtion polymer, which is the desired product, the atom economy will be 100%.
Chloroethene (vinyl chloride), the monomer required to make PVC, can be mIB Docs (2) Teamfactured in industry by thermally cracking 1,2-dichloroethane according to the equation:
ClCH2CH2Cl → CH2=CHCl + HCl
The hydrogen chloride is removed as a waste product. The percentage yield for this cracking process is about 50%.
What is the atom economy for this process?
Every mole of 1,2-dichlorethane that reacts forms one mole of chloroethene (the desired product) and one mole of hydrogen chloride (an undesired product). M(C2H3Cl) = 62.5 g mol−1 and M(HCl) = 36.5 g mol−1 so atom economy = (62.5 ÷ 99.0) x 100 = 63%.
Which poly(ethene) product may be made from low density poly(ethene), LDPE?
Plastic wrap for sealing food items needs to be very thin, relatively strong and very flexible. The side-chains present in molecules of LDPE give it this flexibility.
Which are disadvantages of using plasticizers (e.g. phthalate esters) in polymers such as PVC?
I. Over time the plasticizers may migrate or decompose making the polymer more brittle.
II. Some plasticizers have been shown to have negative effects on the environment and are toxic to humans.
III. Some plasticizers increase the degradation of the polymer by ultraviolet light.
In fact many plasticizers absorb ultraviolet radiation and enhance the life of the polymer by screening ultraviolet light from sunlight which prevents it from breaking down the polymer.
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