Engineering Chemistry MCQ (Elastomers)

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Engineering Chemistry MCQ (Elastomers)

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Elastomers – 1

1. Which of the following is not the essential structural requirement of an elastomer?
a) Long flexible chains
b) Weak intermolecular forces
c) Rigidity in structure
d) Occasional cross-linking
Answer: c
Explanation: Elastomers are a long flexible chain; they are not rigid in nature.

2. Natural rubber is ____________
a) Poly isoprene
b) Ethylene glycol
c) Butadiene
d) Acrylonitrile
Answer: a
Explanation: Natural rubber is poly (cis) isoprene. Malaysia is one of the leading producers of rubber.

3. The structural formula of isoprene is ____________
a) 2-benzyl-1,3-butadiene
b) 2-methyl-1,3-butadiene
c) 3-benzyl-1,2-butadiene
d) 3-methyl-1,2-butadiene
Answer: b
Explanation: The structural formula of isoprene is 2-methyl-1,3-butadiene. It is a
common organic compound with the formula CH2=C(CH3)-CH=CH2. In its pure form,
it is a colorless volatile liquid. Isoprene is produced by many plants.

4. Select the incorrect statement from the following option.
a) Raw rubber is weak and have low tensile strength
b) Raw rubber is attacked by oxidizing agent
c) In organic solvents, it undergoes swelling and disintegration
d) Raw rubber is durable
Answer: d
Explanation: Raw rubber is not durable due to its oxidation in air. All the other options are correct.

5. The temperature at which raw rubber is heated for the vulcanisation process is ____________
a) 0-10 0C
b) 10-50 0C
c) 50-100 0C
d) 100-140 0C
Answer: d
Explanation: The temperature at which raw rubber is heated for the vulcanisation
process is 100-140 0C. A typical vulcanization temperature for a passenger tire is 10 minutes at 177 °C.

6. In the vulcanisation process, the raw rubber is heated with ____________
a) Oxygen
b) Sulphur
c) Carbon
d) Calcium
Answer: b
Explanation: In the vulcanisation process, the raw rubber is heated with sulphur. It is
a chemical process for converting natural rubber or related polymers into more
durable materials via the addition of sulphur or other equivalent curatives or
accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains.

7. The amount of sulphur added determines the extent of stiffness of vulcanised rubber.
a) True
b) False
Answer: a
Explanation: The amount of sulphur added determines the extent of the stiffness of
vulcanised rubber. This sulphur modify the polymer by forming cross-links (bridges) between individual polymer chains.

8. Select the incorrect statement from the following option.
a) Vulcanised rubber has excellent resilience
b) Vulcanised rubber has only slight tackiness
c) Vulcanised rubber has high elasticity
d) Vulcanised rubber has tensile strength 10 times more than raw rubber
Answer: c
Explanation: Vulcanised rubber has low elasticity and decreases with the extent of
vulcanisation. All the other options are correct.

9. The tensile strength(kg/cm 2) of vulcanised rubber is ____________
a) 200
b) 2000
c) 500
d) 5000
Answer: b
Explanation: The tensile strength of vulcanised rubber is 2000 kg/cm 2. Cross-linking
introduced by vulcanization prevents the polymer chains from moving independently.

10. The percentage of butadiene and styrene in Buna-S is ____________
a) 50% each
b) 60% and 40% respectively
c) 80% and 20% respectively
d) 75% and 25% respectively
Answer: d
Explanation: The percentage of butadiene and styrene in Buna-S is 75% and 25%
respectively. These materials have good abrasion resistance and good aging stability when protected by additives.


Elastomers – 2

1. Which of the following act as a catalyst in the preparation of Buna-S?
a) Benzoyl peroxide
b) Hydrogen peroxide
c) Cumene hydroperoxide
d) Acrylonitrile
Answer: c
Explanation: Cumene hydroperoxide act as a catalyst in the preparation of Buna-S (Butadiene styrene).

2. Which of the following statement is incorrect about the SBR?
a) It has low load bearing capacity
b) It has high abrasion resistance
c) It swells in oils and solvents
d) It has low oxidation resistance
Answer: a
Explanation: SBR has high load bearing capacity, high abrasion resistance, swells in oil and solvent and has low oxidation resistance.

3. Which of the following is an application of SBR?
a) Conveyor belts for food
b) Lining of tanks
c) Oil-resistance foam
d) Printing rollers
Answer: b
Explanation: Lining of tanks, adhesives, gaskets, motor tyres, etc are some of the applications of SBR.

4. Buna-N is prepared by co-polymerisation of butadiene and acrylonitrile in the emulsion system.
a) True
b) False
Answer: a
Explanation: Buna-N is prepared by the co-polymerisation of butadiene and
acrylonitrile in the emulsion system. Buna-N is nitrile rubber used in the automotive
and aeronautical industry to make fuel and oil handling hoses.

5. Which of the following has the best resistance to oils?
a) Natural rubber
b) Neoprene
c) Nitrile rubber
d) Styrene rubber
Answer: c
Explanation: Nitrile rubber has the best resistance to oils among the following
options. All the other options have lower resistance to oils.

6. Which of the following is not an application of neoprene?
a) Conveyor belts
b) Wire and cable insulation
c) Adhesives
d) Printing rollers
Answer: d
Explanation: Conveyor belts, adhesives, wire and cable insulation, shoe-soles, etc
are some of the applications of neoprene. Printing rollers is not an application of neoprene.

7. The major constituent of butyl rubber is ____________
a) Isobutylene
b) Isoprene
c) Chloroprene
d) Acrylonitrile
Answer: a
Explanation: In butyl rubber, isobutylene constitutes (95-99) % and isoprene constitutes (1-5) %.

8. Which of the following act as a catalyst in the preparation of butyl rubber?
a) Cumene hydroperoxide
b) Anhydrous AlCl3
c) Lewis base
d) Grignard reagent
Answer: b
Explanation: Anhydrous AlCl3 acts as a catalyst in the preparation of butyl rubber.
Butyl rubber is a synthetic rubber, a co-polymer of isobutylene with isoprene.

9. The solvent used in the preparation of butyl rubber is ____________
a) Methyl iodide
b) Methyl halide
c) Methyl chloride
d) Methyl sulphide
Answer: c
Explanation: The solvent used in the preparation of butyl rubber is methyl chloride.
Butyl rubber is a synthetic rubber, a copolymer of isobutylene with isoprene.

10. Because of its hydrocarbon nature, butyl rubber is soluble in hydrocarbon solvents but has excellent resistance to polar solvents like alcohol and acetone.
a) True
b) False
Answer: a
Explanation: Because of its hydrocarbon nature, butyl rubber is soluble in
hydrocarbon solvents but has excellent resistance to polar solvents like alcohol and
acetone. Butyl rubber and halogenated rubber are used for the inner liner that holds the air in the tire.