Multiple choice question for engineering
Set 1
1. Which of the following is used as a catalyst for the alkylation of benzene in the process of formation of styrene?
a) AlCl3
b) MgO
c) FeO
d) TiCl4
Answer
Answer: a [Reason:] The alkylation of benzene involves the use of Friedel-Crafts catalysts AlCl3 for the formation of ethyl benzene which would further produce styrene.
2. Which of the following can stabilize the vinyl benzene?
a) t-butyl catechol
b) t-butyl hexanol
c) lactone
d) none of the mentioned
Answer
Answer: a [Reason:] Styrene, also known as vinyl benzene, is stabilized by the addition of traces of phenolic stabilizer, like t-butyl catechol after it is separated from the dehydrogenated product by distillation. It is then stored in a cold storage for longer-shelf life.
3. How many stages do the bulk polymerization of styrene passes through?
a) 2
b) 1
c) 3
d) 4
Answer
Answer: a [Reason:] The bulk or mass polymerization of styrene takes place in two stages. In the first stage, the stabilizer free monomer is polymerized to a low conversion in a CSTR. Then, in the next stage, high conversion takes place in a tower reactor (25-40 ft high and 15 ft diameter) with increasing temperature gradient.
4. What kind of polymer is the commercially used polystyrene?
a) syndiotactic
b) isotactic
c) atactic
d) all of the mentioned
Answer
Answer: c [Reason:] Commercial Polystyrene is generally linear atactic polymer, which in amorphous and transparent in nature.
5. Which of the following property of polystyrene is improved, when traces of unreacted monomer is removed?
a) melting point
b) brittleness
c) crystallinity
d) none of the mentioned
Answer
Answer: a [Reason:] The melting point or heat distortion temperature is improved from nearly 70 to 100 ᵒC, by removing the last traces of unreacted monomer from the polymer formed.
6. What is the approximate density of polystyrene in g/cm3?
a) 0.96
b) 0.915
c) 1.054
d) 1.5
Answer
Answer: c [Reason:] The density of polystyrene is nearly 1.054 g/cm3, which is quite higher than the densities of polyethylene and polypropylene.
7. Polystyrene is not a suitable polymer to be used for injection moulding and thermoforming. State true or false.
a) true
b) false
Answer
Answer: b [Reason:] Polystyrene is an ideal polymer to be used for injection moulding and thermoforming, due to its properties like, low moisture absorption, dimensional stability, low moulding shrinkage and good mouldability.
8. Which of the following grade of polystyrene is useful in optical applications?
a) general-purpose (GP-PS)
b) high impact (HIPS)
c) expanded grades
d) none of the mentioned
Answer
Answer: a [Reason:] The GP-PS polymer produced is used for optical applications because of its excellent optical properties with high refractive index.
9. What is the effect of the outdoor exposure on polystyrene?
a) lowering of melting point
b) crazing and yellowing
c) increased brittleness
d) none of the mentioned
Answer
Answer: b [Reason:] Polystyrene has poor outdoor weathering resistance and it crazes and turns yellow after long use.
10. Which component is present in the high impact polystyrene (HIPS) besides styrene monomer to improve only impact strength of polystyrene?
a) acrylo-nitrile
b) vinyl acetate
c) polybutadiene
d) all of the mentioned
Answer
Answer: c [Reason:] HIPS is produced by the emulsion polymerization of monomer with dispersed particles of polybutadiene. The enhancement in impact properties of polystyrene is dependent on the size, concentration and distribution of particles of polybutadiene.
11. Where is the expandable grade of polystyrene useful in?
a) producing foamed products
b) producing rubbery products
c) making optical instruments
d) none of the mentioned
Answer
Answer: a [Reason:] The expandable grade of polystyrene is used to produce foamed products. The beads of expanded polystyrene is formed by suspension polymerization of styrene in the presence of volatile organic foaming or blowing agents, like pentane or hexane.
12. Which of the following properties is improved when styrene and acrylo-nitrile are copolymerized together?
a) heat distortion temperature
b) impact strength
c) chemical resistance
d) all of the mentioned
Answer
Answer: d [Reason:] To improve the impact strength and the heat distortion temperature of styrene-based polymer, styrene is copolymerized with 20-30% acrylo-nitrile. The copolymer formed has better chemical and solvent resistance, and also better resistance to stress cracking and crazing.
13. Which of the following comonomer can copolymerize with styrene to give out a polymer suitable for making ion-exchange resins?
a) vinyl acetate
b) divinyl benzene
c) acrylonitrile
d) butadiene
Answer
Answer: b [Reason:] The polymer based on styrene that is used in making ion-exchange resins is produced in the cross-linked form by suspension polymerization of styrene and comonomer divinyl benzene.
14. What is the percentage value of elongation at break for polystyrene?
a) 1-3%
b) 100-300%
c) 20-130 %
d) 200-240%
Answer
Answer: a [Reason:] The value of elongation at break for general purpose polystyrene is 1-3%, which is comparatively very low as compared to other polymers.
15. Which of the following grade of polystyrene is well suited for the purpose of packaging applications?
a) high impact (HIPS)
b) general purpose (GP-PS)
c) expandable
d) all of the mentioned
Answer
Answer: c [Reason:] The expandable grade is used to produce foamed products. The smaller beads that are foamed provide better mechanistic properties along with surface finish, which makes its use in custom packaging and insulation purposes.
Set 2
1. How does the viscosity vary with the onset of gelation of reaction mixture?
a) increases
b) decreases
c) remains constant
d) none of the mentioned
Answer
Answer: a [Reason:] With the onset of gelation, the medium viscosity increases rapidly and formation of insoluble mass (gel) takes place.
2. The cross linking established by linking the branched units leads to three dimensional structure which gives rise to the phenomenon of gelation of reaction mixture. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] The cross linking of branched units lead to the formation of measurable proportion of insoluble and infusible mass called gel, which then rapidly gets transformed into visco-elastic mass, if reaction continues beyond the gel point.
3. What does f in the expression for critical probability that the branched unit is linked to another branched unit, represents?
a) average functionality
b) functionality of branched units
c) functionality of monomer
d) none of the mentioned
Answer
Answer: b [Reason:] The expression for critical probability is given by,
αc = 1/(f-1)
The f, here represents the functionality of branched units and if more than one branched units differing in functionality are used, then f is the average value of all multi-functional monomers.
4. What is the critical value of probability for trifunctional branch unit?
a) 1
b) 0.5
c) 0.25
d) 0.7
Answer
Answer: b [Reason:] The critical probability for a trifunctional branch unit is 0.5 and it can be verified using the formula
αc = 1/(f-1).
5. Which of the following assumptions fail taking into account the example of glycerol?
a) equal reactivity of functional groups
b) intramolecular cyclization reactions are forbidden
c) all of the mentioned
d) none of the mentioned
Answer
Answer: a [Reason:] Glycerol contains three hydroxyl groups where secondary hydroxyl is less reactive than other two primary hydroxyl groups. This violates the assumption of equal reactivity.
6. The Carothers’ equation is used to predict the extent of polycondensation reaction at which the average degree of polymerization Xn, becomes infinite. State true or false.
a) True
b) False
Answer
Answer: a [Reason:] W.H. Carothers derived a general expression, relating the average functionality, extent of reaction and degree of polymerization, which is known as Carothers’ equation
p= (2/f)(1-1/ Xn).
7. Why is it advisable to stop the reaction nearly 10-15% earlier the critical reaction completion?
a) cross-linking occurs
b) to avoid damage of reaction bowl
c) insoluble, bad quality product is obtained
d) all of the mentioned
Answer
Answer: d [Reason:] If the reaction continues beyond the critical point, the product obtained will be unusable. So, it is advised to stop the reaction 10-15% earlier in p to avoid all the above problems and get good quality product.
8. Which curve represents the gel formation in the following graph, for a trifunctional polycondensation
a) 1
b) 2
c) 3
d) 4
Answer
Answer: d [Reason:] For a trifunctional system, gelation start at p=0.5, and at p=1, the whole system is converted into insoluble and infusible mass of a giant molecule. So curve 4 represents the gelation process.
Set 3
1. Which of the following can activate chain initiation?
a) heat
b) light or radiation
c) catalysts
d) all of the mentioned
Answer
Answer: d [Reason:] The chain initiation can be induced by heat, light or energy radiations or with the help of initiators or catalysts.
2. Which of the following monomers cannot undergo chain growth polymerization?
a) CH2═ CH2
b) CH2═CHCN
c) CH2═CHCOOR
d) COOH−CH2−COOH
Answer
Answer: d [Reason:] Dicarboxylic acid undergoes condensation polymerization.
3. Why is addition polymerization also known as vinyl polymerization?
a) monomers are unsaturated compounds
b) its a chain reaction
c) most monomers contain (CH2═CH─) group
d) all of the mentioned
Answer
Answer: c [Reason:] Most of the monomers involves in chain polymerization contains (CH2═CH─) group, which is commonly known as vinyl group.
4. Which of the following cannot initiate the chain reaction in polymerization of acrylo-nitrile?
a) anion
b) cation
c) free radical
d) coordination
Answer
Answer: b [Reason:] Acrylonitrile contains ─CN group which is an electron withdrawing group and cannot adopt a cationic pathway. Anion, free radical and coordination complex can polymerize it to high molecular weight polymer.
5. What does chain initiation step of free radical polymerization consists of?
a) decomposition of initiator
b) addition of free radical to monomer
c) all of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] The first step in chain initiation is decomposition of initiator to free radicals and the second step is addition of free radical to the monomer unit.
6. Which is the rate determining step of chain initiation step?
a) initiator decomposition
b) chain initiation of monomer
c) chain propagation
d) none of the mentioned
Answer
Answer: a [Reason:] Initiator decomposition step is the rate determining step of chain initiation step as it is the slowest of two.
7. Which mode in the chain termination step is accompanied by a transfer of hydrogen molecule?
a) combination
b) disproportionation
c) propagation
d) all of the mentioned
Answer
Answer: b [Reason:] The disproportionation mode of termination is accomplished by a hydrogen transfer from one radical molecule to other, which is given by-
R~~~ CH2−∙CHX + XH∙C−CH2 ~~~~~R → R ~~~ CH2− CH2X + R~~~ CH═CHX.
8. The substance that is so effective, which can suppress the rate as well as degree of polymerization is a ___________
a) retarder
b) inhibitor
c) promoter
d) none of the mentioned
Answer
Answer: b [Reason:] If an inhibitor is added to a monomer, then it may reduce the rate of reaction and may even suppress degree of polymerization.
9. Which of the following mechanism can occur for the termination step to take place?
a) combination
b) disproportionation
c) all of the mentioned
d) none of the mentioned
Answer
Answer: c [Reason:] Combination and disproportionation both are the modes of termination step of free radical polymerization.
10. Which of the following factors does termination mechanism depend on?
a) type of active centre
b) nature of monomer
c) reaction conditions
d) all of the mentioned
Answer
Answer: d [Reason:] The convenient mechanism for chain termination largely depends on all the above factors.
Set 4
1. Which synthetic rubber is also commonly known as hypalon?
a) polychloroprene rubber
b) chloro-sulphonated polyethylene
c) styrene-butadiene rubber
d) nitrile rubber
Answer
Answer: b [Reason:] Chlorosulphonated polyethylene (CSP) is commonly known in the trade as Hypalon.
2. What kind of synthetic rubbers are commonly known as thiokols?
a) polyurethane rubbers
b) polysulphide rubbers
c) fluorocarbon rubbers
d) polyacrylic rubbers
Answer
Answer: b [Reason:] Polysulphide rubbers are commonly known as Thiokols due to the presence of thio group in their structure.
3. What is the cis content of polybutadiene rubber obtained by emulsion polymerization using redox catalyst?
a) <40%
b) >10%
c) >92%
d) None of the mentioned
Answer
Answer: b [Reason:] Polybutadiene prepared by emulsion polymerization in the presence of redox catalysts is lower in cis content i.e. below 10%.
4. Which of the following catalyst is used to obtain polybutadiene of cis content <40%?
a) coordination catalyst based on Ni, Co
b) redox catalyst
c) zeiglar natta catalyst
d) butyl lithium catalyst
Answer
Answer: d [Reason:] When polybutadiene is prepared using butyl lithium catalyst, rubber of lower cis content (<40%) is formed. Using coordination catalyst, high cis content (>90%) polybutadiene is obtained.
5. Which synthetic rubbers are blended with BR to make its extensive use in tyres?
a) NR and SBR
b) NBR and SBR
c) NR and NBR
d) NR, NBR and SBR
Answer
Answer: a [Reason:] BR is blended with natural rubber and SBR in the manufacture of tyres for improved milling, wet skid resistance, while BR imparts excellent abrasion resistance to car and truck tyres.
6. Consider the following statements about emulsion SBR and solution SBR.
I. Solution SBR has higher content of non-rubber materials than emulsion SBR
II. Solution SBR has higher molecular weight but broader molecular weight distribution than emulsion SBR
III. Solution SBR has higher cis-1,4-polybutadiene content than emulsion SBR
Which of the following statements are true?
a) I, II, III
b) I, II
c) III only
d) I only
Answer
Answer: c [Reason:] Solution SBR has a lower content (nearly 2%) of non-rubber materials while emulsion SBR has non-rubber materials in excess of 10%. Solution SBR has narrower molecular weight distribution, higher cis-1,4-polybutadiene content and higher molecular weight than emulsion rubber.
7. What are the temperature conditions for production of hot emulsion SBR and cold emulsion SBR, respectively?
a) 50-60 ᵒC and 5 ᵒC
b) 80-90 ᵒC and 5 ᵒC
c) 50-60 ᵒC and 10 ᵒC
d) 80-90 ᵒC and 10 ᵒC
Answer
Answer: a [Reason:] Polymerization of butadiene and styrene carried out at 50-60 ᵒC gives hot emulsion SBR and when it is carried out at 5 ᵒC using appropriate redox initiators gives a product known as cold emulsion SBR.
8. Which configuration of butadiene units is present in highest amount in SBR at 50 ᵒC?
a) trans-1,4
b) cis-1,4
c) cis-1,2
d) all of the mentioned
Answer
Answer: a [Reason:] The butadiene units in SBR are composed of approximately 15-20% of cis-1,4; 60-70% of trans-1,4; and 15-20% of 1,2 configuration for the polymer. The rubbers produced at low temperatures generally have higher content of trans-1,4 butadiene units.
9. What is the correct order of the poor resilience characteristics in the given rubbers?
a) NR>SBR>BR
b) BR>NR>SBR
c) SBR>BR>NR
d) BR>SBR>NR
Answer
Answer: b [Reason:] Butadiene rubbers have high resilience characteristics than natural rubber while SBR have poor resilience characteristics as compared to natural rubber. Therefore, the order follows BR>NR>SBR.
10. What is the IUPAC name of the monomer of polychloroprene?
a) 2-chloro-1,3-butadiene
b) 3,4-dichlorobut-1-ene
c) 1-chloro-1,3-butadiene
d) none of the mentioned
Answer
Answer: a [Reason:] The monomer of Polychloroprene is chloroprene whose IUPAC name is 2-chloro-1,3-butadiene.
11. Which type polymerization is used to produce Polychloroprene commercially?
a) solution polymerization
b) bulk polymerization
c) emulsion polymerization
d) all of the mentioned
Answer
Answer: c [Reason:] polychloroprene is produced commercially by emulsion polymerization using soap such as rosin soap.
12. Which material is made to react with polymer latex of polychloroprene to set a desired plasticity when modification with sulphur is done?
a) tricresyl phosphate
b) triethylthiuram sulphide
c) tetraethylthiuram sulphide
d) dioctyl phthalate
Answer
Answer: c [Reason:] Certain grades of polymer are modified using sulphur as a crosslinkin-agent where the latex, after completion of polymerization, is allowed to stand and react with tetraethylthiuram sulphide to restore desired plasticity of the polymer.
13. Which of the following feature is responsible for the crystallizable nature of neoprene?
a) 1,4-trans structure
b) 1,4-cis structure
c) all of the mentioned
d) none of the mentioned
Answer
Answer: a [Reason:] Neoprene has an overwhelmingly 1,4-trans structure and this structural feature is responsible for its crystallizable nature.
14. What is the average curing mixture for the vulcanization of Polychloroprene rubber (CR)?
a) 5 parts ZnO and 4 parts MgO per 100 parts of neoprene
b) 4 parts ZnO and 5 parts MgO per 100 parts of neoprene
c) 8 parts sulphur per 100 parts of neoprene
d) 10 parts sulphur per 100 parts of sulphur
Answer
Answer: a [Reason:] Vulcanization of CR is more conveniently accomplished with zinc oxide and magnesium oxide rather than using sulphur or sulphur donor compounds. 5 parts ZnO and 4 parts MgO per 100 parts of neoprene are used as the average curing mixture.
15. Most filled technical Cr compounds show better resilience than NR of similar loading. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] With increasing filler loading in NR and CR compounds, however, the resilence drops, though to a lesser content for CR system. This is why, most filled CR compounds show better resilence than NR of similar loading.
Set 5
1. Which of the following initiation mechanism in vinyl polymerization, does not produce a pure polymer?
a) initiator decomposition
b) uncatalyzed thermal initiation
c) uncatalyzed photochemical initiation
d) all of the mentioned
Answer
Answer: a [Reason:] For uncatalyzed vinyl polymerization done thermally or photochemically, the polymer produced is very pure and free from any contaminants, while the use of initiator leaves the polymer impure due to the presence of traces of initiator in it.
2. What may be the consequence of the uncontrolled vinyl polymerization with excessive rise in temperature?
a) discolouration
b) thermal degradation
c) branching or cross-linking
d) all of the mentioned
Answer
Answer: d [Reason:] If reaction is left uncontrolled, excessive increase in the temperature at local points called ‘hotspots’ can cause discolouration, thermal degradation, branching of polymers and sometimes even cross-linking, giving rise to the formation of polymer of inferior quality.
3. Why does heat dissipation in bulk polymerization becomes progressively difficult with high conversions?
a) increase in medium viscosity
b) solubilization of polymer in the monomer
c) precipitation of polymer in the monomer
d) all of the mentioned
Answer
Answer: d [Reason:] The stirring process and heat dissipation become progressively difficult due to gain in viscosity medium or due to solubilization or precipitation of polymer in the monomer, more so in higher conversions.
4. Which of the following monomer mixture is used in bulk polymerization?
a) undiluted monomer
b) monomer –solvent mixture
c) monomer-water mixture
d) none of the mentioned
Answer
Answer: a [Reason:] Bulk polymerization is the polymerization of undiluted monomer and is the simplest technique of polymer synthesis.
5. How is the solvent in solution polymerization, more useful to overcome the disadvantages of bulk polymerization?
a) it reduces the viscosity gain
b) increases the rate of reaction
c) causes chain transfer
d) all of the mentioned
Answer
Answer: a [Reason:] The solvent reduces the viscosity gain, thus allowing more efficient stirring of the medium and proper heat dissipation of the heat liberated. The chain transfer to solvent causes a problem for solution polymerization.
6. Which of the following is a demerit of solution polymerization?
a) handling of inflammable solvents
b) recovery of solvent
c) chain transfer to solvent
d) all of the mentioned
Answer
Answer: d [Reason:] The solution polymerization process often requires the handling of inflammable solvents and the recovery of solvent from the polymer to isolate it. Chain transfer to solvent may also pose a problem as the purity of polymer is affected due to the leftover traces of solvent in the polymer product.
7. Which of the following polymerization system prepared by solution polymerization, is heterogeneous in character?
a) methyl methacrylate in solvent
b) acrylonitrile in organic solvent
c) ethylene in organic solvent
d) all of the mentioned
Answer
Answer: b [Reason:] In polymerization of acrylonitrile in water or any organic solvent, the solvent is not able to dissolve the polymer being formed and so the system becomes heterogeneour in nature with polymer formation.
8. Which of the following polymerization is also known as pearl polymerization?
a) bulk polymerization
b) solution polymerization
c) emulsion polymerization
d) suspension polymerization
Answer
Answer: d [Reason:] At the end of the suspension polymerization, the polymer formed appears in the form of tiny beads or pearls, so it is also known as pearl polymerization.
9. What kind of initiators is used in the process of suspension polymerization?
a) oil-soluble
b) water-soluble
c) oil-water insoluble
d) none of the mentioned
Answer
Answer: a [Reason:] In suspension polymerization, oil-soluble initiators like peroxides, hydroperoxides and azo-compounds are used.
10. Which of the following is used as a stabilizer in suspension polymerization?
a) gelatin
b) peroxides
c) water
d) carbon tetrachloride
Answer
Answer: a [Reason:] The process of suspension polymerization requires water soluble polymer stabilizers like CMC, PVA or gelatin, etc. to raise medium viscosity and stabilize the suspension.
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