IMO Practice Test — Polymers
14 Questions • 15 min • Olympiad level
15:00
Question 1 of 14
A polymer that softens on heating and can be remoulded repeatedly, with no significant cross-linking, is best classed as a:
thermoplastic
thermosetting polymer
elastomer
fibre
Explanation: Remouldable, lightly bonded polymers are thermoplastics.
Question 2 of 14
A condensation polymer is identified by the fact that on forming each linkage it:
gains a double bond
absorbs heat only
eliminates a small molecule
loses a radical
Explanation: Step-growth condensation eliminates a small molecule (e.g. water) per linkage.
Question 3 of 14
If the repeating unit of a polymer is -(CF2-CF2)-, the monomer is:
CHF=CHF
CH2=CHF
CF2=CF2
CCl2=CCl2
Explanation: The repeating -(CF2-CF2)- comes from tetrafluoroethene, CF2=CF2 (Teflon).
Question 4 of 14
The order of increasing intermolecular forces is:
elastomers < thermoplastics < fibres
fibres < thermoplastics < elastomers
thermoplastics < elastomers < fibres
fibres < elastomers < thermoplastics
Explanation: Elastomers have the weakest and fibres the strongest intermolecular forces.
Question 5 of 14
A polymer made from a single bi-functional cyclic monomer that ring-opens on heating is:
nylon-6,6
terylene
nylon-6
Buna-S
Explanation: Nylon-6 forms from caprolactam by ring-opening polymerisation.
Question 6 of 14
During free-radical propagation, the number of radical centres in the system:
increases by one per step
decreases by one per step
stays essentially constant
becomes zero
Explanation: Each propagation regenerates one radical at the chain end, so the count is roughly constant until termination.
Question 7 of 14
Which pair of monomers will undergo condensation polymerisation?
CH2=CH2 and CH2=CHCl
CF2=CF2 and CH2=CH-CN
HOOC-(CH2)4-COOH and H2N-(CH2)6-NH2
CH2=CH2 and styrene
Explanation: A diacid and a diamine condense (loss of water) to a polyamide; the other pairs are unsaturated monomers for addition.
Question 8 of 14
Vulcanised rubber is harder than natural rubber primarily because sulphur:
removes the double bonds entirely
increases the chain length
forms cross-links between chains
acts only as a filler
Explanation: Sulphur cross-links restrict chain slippage, raising strength and hardness.
Question 9 of 14
Which of the following is NOT an addition polymer?
polythene
PVC
Teflon
nylon-6,6
Explanation: Nylon-6,6 is a condensation polymer; the rest are addition polymers.
Question 10 of 14
A copolymer that is oil-resistant and used in fuel hoses is:
Buna-S
neoprene
Buna-N
polythene
Explanation: Buna-N (butadiene-acrylonitrile) is oil- and chemical-resistant.
Question 11 of 14
For a polymer sample, the polydispersity index (Mw/Mn) equals 1 only when:
all chains have the same molecular mass
the chains are highly branched
cross-linking is complete
the polymer is biodegradable
Explanation: PDI = 1 means a perfectly uniform sample with identical chain lengths.
Question 12 of 14
Glycine and aminocaproic acid are the monomers of the biodegradable polymer:
PHBV
Dacron
bakelite
nylon-2-nylon-6
Explanation: Nylon-2-nylon-6 is a biodegradable polyamide of glycine and aminocaproic acid.
Question 13 of 14
The chief difference between LDPE and HDPE in synthesis is that HDPE uses:
a higher pressure
oxygen as initiator
a Ziegler-Natta catalyst at low pressure
ultraviolet light
Explanation: HDPE uses a Ziegler-Natta catalyst at low pressure, giving linear, close-packed chains.
Question 14 of 14
Strong hydrogen bonding between -CONH- groups in nylon explains its:
elasticity
low melting point
thermosetting behaviour
high tensile strength and fibre nature
Explanation: Inter-chain hydrogen bonding gives close packing, high tensile strength and thread-forming ability.