Multiple choice question for engineering
Set 1
1. What is the mechanism of uncatalyzed photo-initiation of polymerization, when light of specific wavelength falls on monomer?
a) monomer directly decomposes to give radicals
b) monomer generates excites species by absorbing light quanta and then decompose into radicals by homolysis
c) photo-initiator is added to monomer and decomposes to radicals by photolysis
d) all of the mentioned
Answer
Answer: b [Reason:] The monomer, on photo-activation, generates excited species M*, by absorbing the light quanta of specific wavelength and the subsequently decomposes to give radicals by homolysis.
2. What has the terms kd[I] in the overall rate equation of uncatalyzed photo-polymerization been replaced by?
a) intensity of light radiation absorbed
b) intensity of incident light
c) number of pairs of chain radicals formed per quantum of light absorbed
d) monomer concentration
Answer
Answer: a [Reason:] The term kd[I] is replaced by the intensity of active radiation absorbed, Ia and f is replaced by φ that stands for number of pairs of chain radicals formed per quantum of light absorbed.
3. What does the intensity of active radiation absorbed in uncatalyzed photo-polymerization, not depend on?
a) thickness of reaction mixture
b) intensity of incident radiation
c) monomer concentration
d) none of the mentioned
Answer
Answer: a [Reason:] The intensity of incident light does not vary measurably with the thickness of reaction mixture, while it is proportional to the product of intensity of incident radiation and monomer concentration.
4. How does the overall rate of uncatalyzed photo-polymerization vary, when the monomer concentration is quadrupled, rest all the terms remain same?
a) two fold increase
b) eight fold increase
c) remains same
d) two fold decrease
Answer
Answer: b [Reason:] According to the rate expression of uncatalyzed photo-polymerization, we have
Rp α [M]1.5
Therefore, when monomer concentration is quadrupled, Rp increases by 8 times.
5. Which of the following initiator system works on the mechanism of photo-activation?
a) hydrogen halide
b) nitrobenzene complexes
c) hydrogen sulphide
d) oxalate complex of transition metals
Answer
Answer: c [Reason:] The cleavage of H─S bond in hydrogen sulphide takes place by photo-activation, which then gives H∙ and HS∙ radicals.
6. Photo-activation allows the use of a wide range of chemicals as polymerization initiators in comparison to the thermal catalyzed process. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] This happens because of the high selectivity of photolytic homolysis in most compounds.
7. What is the expression for rate of initiation in catalyzed photo-polymerization? ( I0 and φ are the intensity of incident light and number of pairs of chain radicals formed per quantum of light absorbed, respectively and ε be the molar absorption coefficient )
a) 2φεI0[I]
b) φεI0[M]
c) 2φεI0[M]
d) φεI0[I]
Answer
Answer: a [Reason:] The rate of initiation in catalyzed photo-polymerization, when a photo-initiator, I is used, is given by-
Ri = 2φεI0[I].
8. Which of the following is not true about photo-sensitizer in photo-polymerization?
a) easily gets excited on exposure to light
b) carries energy absorbed to initiator or monomer
c) helps in both catalyzed and uncatalyzed polymerizations
d) gets excited and decomposes to give radicals
Answer
Answer: d [Reason:] Photo-sensitizer gets easily excited on exposure to light, and the carries adsorbed light to initiator and monomer molecules so that they undergo homolysis to reduce chain-initiating radicals.
9. What happens to overall rate of catalyzed photo-polymerization, when the initiator concentration is quadrupled?
a) doubled
b) quadrupled
c) tripled
d) remains same
Answer
Answer: a [Reason:] According to the rate expression of related photo-polymerization, we have
Rp α [I]0.5
Therefore, Rp gets doubled.
Set 2
1. At what temperature does acetylene reacts with dry hydrogen chloride in a multi tubular reactor packed with mercuric chloride catalyst, supported over activated carbon, to produce vinyl chloride?
a) 50-60 ᵒC
b) 90-100 ᵒC
c) 150-175 ᵒC
d) 180 ᵒC
Answer
Answer: b [Reason:] The acetylene and dry hydrogen chloride mixture is added to the multi tubular reactor, temperature of which is maintained at 90-100 ᵒC. The reactor bed packed with mercuric chloride catalyst is supported over by activated carbon support.
2. Which of the following reaction does not give HCl as a byproduct?
a) oxychlorination of ethylene
b) hydrochlorination of acetylene
c) chlorination of ethylene
d) none of the mentioned
Answer
Answer: b [Reason:] Hydrochlorination of acetylene does not give HCl as a byproduct. The reaction is-
CH≡CH + HCl → CH2═CH−Cl
In the rest other reactions after cracking of ethylene di-chloride, HCl is removed as a byproduct of the reaction.
3. Which of the following grades of poly vinyl chloride is unsuitable for insulation purposes?
a) bulk grade
b) suspension grade
c) emulsion grade
d) none of the mentioned
Answer
Answer: c [Reason:] The emulsion grade of PVC contains some traces of soap or detergent and other ionic components, which makes it unsuitable to be used in insulation industry.
4. What approx. percentage of chlorine is present in the homopolymer of vinyl chloride?
a) 57%
b) 50%
c) 48%
d) 40%
Answer
Answer: a [Reason:] The homopolymer of vinyl chloride contains nearly 57% chlorine. By increasing the chlorine content in PVC, its heat deflection temperature can be increased.
5. Which of the following solvent cannot solubilize Poly vinyl chloride into it?
a) cyclohexanone
b) tetra hydrofuran
c) hexane
d) nitrobenzene
Answer
Answer: c [Reason:] Poly vinyl chloride is insoluble in all hydrocarbon solvents. Therefore, it is insoluble in hexane solvent. On the other hand, PVC is soluble in cyclohexanone, tetrahydrofuran and nitrobenzene.
6. Which of the following property is enhanced when vinyl chloride is copolymerized with 10-20% diethyl fumarate?
a) toughness
b) solubility
c) clarity
d) transparency
Answer
Answer: a [Reason:] Copolymer of vinyl chloride and 10-20% diethyl fumarate has come up with enhanced wokability and toughness, while maintaining the higher softening temperature.
7. Which among the following comonomer can make the copolymer of vinyl chloride suitable for phonograph records?
a) vinyl acetate
b) vinylidene chloride
c) diethyl fumarate
d) diethyl maleate
Answer
Answer: a [Reason:] The copolymer of vinyl chloride and about 13% vinyl acetate is used for phonograph records, due to its low softening temperature and high solubility, better color and clarity.
8. Which of the following compounds can process the flexibility applications of PVC?
a) stabilizers
b) lubricants
c) plasticizers
d) coloring matters
Answer
Answer: c [Reason:] The proper use of plasticizers in poly vinyl chloride can produce flexible items and can process the flexibility applications of PVC. Some of the plasticizers are high boiling phthalates and phosphate plasticizers.
9. Which of the following compound is used in fire retardant compounds of PVC?
a) dibutyl sebacate
b) dibutyl phthalate
c) barium phenate
d) tricresyl phosphate
Answer
Answer: d [Reason:] Tricresyl phosphate is a phosphate plasticizer, which is used in the fire retardant compounds. Chlorinated paraffin and phosphate plasticizers are basically used for this purpose.
10. Which of the following monomer pairs forms a copolymer that exhibits excellent chemical resistance and self-extinguishing properties?
a) vinyl chloride + vinylidene chloride
b) vinyl chloride + vinyl acetate
c) vinyl chloride + acrylonitrile
d) none of the mentioned
Answer
Answer: a [Reason:] Copolymer of 15% vinyl chloride and 85% vinylidene chloride, known as Saran in the trade, has excellent chemical inertness including resistance to acids and alkalies and prominent self-extinguishing properties.
Set 3
1. Name the polymer formed by the polymerization of ω-amino caproic acid using water as a catalyst?
a) nylon 6
b) nylon 6,6
c) nomex
d) abs
Answer
Answer: a [Reason:] Nylon 6 is formed by the polymerization of ω-amino caproic acid in the presence of water ( used as a catalyst) and small amount of acetic acid for regulating the chain length.
nNH2−(CH2)5−COOH → [−NH−(CH2)5−CO−]n .
2. What is the monomer pair required for the formation of Nylon 610?
a) ω-amino caproic acid + diamine
b) hexamethylene diamine + adipic acid
c) hexamethylene diamine + sebacic acid
d) hexamethylene diamine + decanoic acid
Answer
Answer: c [Reason:] The reaction between hexamethylene diamine and sebacic acid gives the polyamide Nylon 610 via formation of an appropriate salt. The reaction is given by-
nNH2−(CH2)6−NH2 + HOOC−(CH2)8−COOH → [−NH−(CH2)6−NH−CO−(CH2)8−CO−]n.
3. Monomer A is reacted with a monomer B in boiling methanol to form a salt. The salt dissolved in water with a little amount of acetic acid is then processed in autoclave at different temperatures and pressure. Monomer A is a bifunctional monomer having amine groups. What is the name of monomer B?
a) adipic acid
b) ω-amino caproic acid
c) undecanoic acid
d) dodecyl lactam
Answer
Answer: a [Reason:] Monomer A is adipic acid and monomer B is hexamethyelene diamine, which reacts in the given conditions and then processed into an autoclave, where temperature is raised to 220 ᵒC and later pressure is allowed to develop at 250 psi.
4. Which of the following mechanism takes place for the formation of high molecular weight Nylon 6 from caprolactum?
a) anionic mechanism
b) cationic mechanism
c) radical mechanism
d) none of the mentioned
Answer
Answer: a [Reason:] The polymerization of caprolactum y anionic mechanism follows in the presence of a strong base to for high molecular weight nylon 6.
5. Which of the following polyamides are known as aramids?
a) aliphatic polyamides
b) aromatic polyamides
c) unsaturated polyamides
d) all of the mentioned
Answer
Answer: b [Reason:] Aromatic polyamides are commonly known as aramids. Aramid fibres are a recent development to be practically used.
6. Which of the following can help in achieving the mechanical properties of nylons?
a) plasticizers
b) nucleating agents
c) mould agents
d) impact modifiers
Answer
Answer: b [Reason:] The mechanical properties of nylons are largely dependent on the crystallinity of polymers. Thus, such kind of properties can be developed by increasing the degree of crystallinity and spherulite size with the help of nucleating agents.
7. Polyamides have a limited use in the areas where long exposure to temperatures above 70-90 ᵒC is required, due to their tendency of surface oxidation in air. Which heat stabilizer can permit their use even in higher temperatures?
a) sodium salts
b) copper salts
c) potassium salts
d) none of the mentioned
Answer
Answer: b [Reason:] The addition of nearly 1% of copper salts acts as heat stabilizer and permits the use of polyamides at higher temperatures.
8. Where is the use of nylon films unsuitable, considering the properties required for applications?
a) packaging of food stuffs
b) packaging of drugs
c) for pharmaceuticals
d) none of the mentioned
Answer
Answer: d [Reason:] Nylon films have an impressing feature of low odour transmission which makes it suitable for use in the packaging of food stuffs, drugs and pharmaceuticals.
9. Which polyamide is formed when polymerization of isophthaloyl chloride and m-phenylene diamine takes place?
a) nomex
b) kevlar
c) nylon 6
d) SBR
Answer
Answer: a [Reason:] Nomex is an aramide formed by the solution or interfacial polymerization of isophthaloyl chloride and m-phenylene diamine. It has a melting point of 365 ᵒC.
10. What is the tensile strength exhibited by the moulded objects prepared from nylons?
a) 12000 psi
b) 1200 psi
c) 60000 psi
d) 6000 psi
Answer
Answer: a [Reason:] The moulded objects prepared from nylons have a tensile strength nearly about 12000 psi, which is far higher than the objects from other polymers.
11. Which of the following monomer pair polymerizes to give an aramide?
a) hexamethylene diamine + sebacic acid
b) terephthaloyl chloride + phenylene diamine
c) hexamethylene diamine + adipic acid
d) none of the mentioned
Answer
Answer: b [Reason:] Aromatic polyamides are generally known as aramides. The polymerization reaction of terephthaloyl chloride and phenylene diamine gives an aromatic amide called, Kevlar.
12. Which polyamide can be used as substitute of steel in belted radial tires?
a) kevlar
b) nomex
c) nylon 12
d) nylon 11
Answer
Answer: a [Reason:] Kevlar provides a fibre material, than has strength equal to steel at one-fifth of its weight. So it is used as a substitute for the steel in belted radial tires and also in manufacturing of protective clothing.
13. Which of the following nylons has a lower specific gravity than the others?
a) nylon 6
b) nylon 66
c) both have nearly same
d) none of the mentioned
Answer
Answer: c [Reason:] Nylon 6 and Nylon 66 have nearly same specific gravities which are close to 1.13 and 1.14, respectively.
14. How the viscosity of aromatic polyamide solutions does vary with the increase in volume fraction of polymer formed?
a) Increases always
b) first increases then decreases
c) first decreases then increases
d) decreases always
Answer
Answer: b [Reason:] The aromatic polyamide solutions show an initial increase in the viscosity with increase in volume fraction of polymer followed by a reversal in the trend and an abrupt decrease in viscosity when a critical volume fraction of polymer is exceeded.
Set 4
1. What is the pressure range for the polymerization process of low density polyethylene?
a) 1500-3000 atm
b) 100-1000 atm
c) 50-100 atm
d) 25-50 atm
Answer
Answer: a [Reason:] The polymerization process of ethylene by free radical polymerization takes place under high pressure ranging 1500 to 3000 atm and low temperatures.
2. What range of temperature is generally employed for low density polyethylene formation on kinetic considerations?
a) 25-50 ᵒC
b) 170-250 ᵒC
c) 200-400 ᵒC
d) 50-150 ᵒC
Answer
Answer: b [Reason:] The temperature range for the polymerization reaction is 170-250 ᵒC, on kinetic considerations because on very low temperatures, the radical polymerization goes far too slow for the production of a polymer.
3. What is the allowable quantity of oxygen at a pressure of 2000 atm and temperature of 165 ᵒC for the polymerization process, over which explosion may occur?
a) 0.075%
b) 0.05%
c) 10%
d) 5%
Answer
Answer: a [Reason:] The allowable oxygen at a pressure of 2000 atm and temperature of 165 ᵒC is 0.075%, otherwise explosive reaction may occur giving hydrogen, methane and carbon in main, if the limit is crossed.
4. Which of the following can be used as an initiator for the formation of low density polyethylene (LDPE)?
a) benzoyl peroxide
b) sulphuric acid
c) dithionite ion
d) nitrobenzene
Answer
Answer: a [Reason:] The initiators than can be used for formation of LDPE are peroxides , oxygen or azo-compounds.
5. What is the affect of high pressure on the molecular weight of the polymer product formed?
a) increases
b) decreases
c) no change
d) cannot be determined
Answer
Answer: a [Reason:] The increase in the pressure increases the local concentration of the gaseous monomer in the vicinity of the transient chain radicals and thereby, increases the chances of obtaining higher molecular weight for the polymer product.
6. What is the possible heat of polymerization of ethylene?
a) 800-1000 cal/g
b) 164-180 cal/g
c) 200-400 cal/g
d) none of the mentioned
Answer
Answer: a [Reason:] The heat of polymerization of ethylene is 800-1000 cal/g which is generally higher than other type of monomers.
7. Which of the following oxide works as a catalyst for the formation of high density polyethylene by Philips process?
a) molybdenum oxide
b) chromium oxide
c) titanium oxide
d) calcium oxide
Answer
Answer: b [Reason:] The Philips process uses CrO3 (5%) supported on finely divided aluminium-silica base as a catalyst , which is dispersed in a hydrocarbon solvent like cyclohexane.
8. Which of the following are used as a promoter in the Standard Oil process for formation of HDPE?
a) sodium hydride
b) hydrogen halide
c) sulphuric acid
d) molybdenum oxide
Answer
Answer: a [Reason:] The Standard Oil process uses the dispersion of molybdenum oxide containing sodium and calcium hydride as promoters in hydrocarbon solvent, at suitable temperature.
9. Which of the following process employs highest range of temperature for the formation of HDPE?
a) ziegler process
b) phillips process
c) indiana process
d) none of the mentioned
Answer
Answer: c [Reason:] The Indiana process is operated at a temperature range of 220-250 ᵒC, whereas the Zeigler process and the Phillips process employs a temperature range of 70-100 ᵒC and 130-150 ᵒC, respectively.
10. What is the approximate density of the polymer produced by the Ziegler process of polymerization?
a) 0.945 g/cm3
b) 1.5 g/cm3
c) 0.5 g/cm3
d) 2.0 g/cm3
Answer
Answer: a [Reason:] Ziegler process for formation of HDPE yields the polymers of density of about 0.945 g/cm3.
Set 5
1. Which of the following kind of polymer has the highest percentage in polypropylene?
a) isotactic
b) atactic
c) syndiotactic
d) all of the mentioned
Answer
Answer: a [Reason:] The reaction conditions in the polymerization of propylene are varied so as to favour the formation of isotactic polymers. Commercial polypropylene is 90-97% isotactic.
2. What is the approximate density of the polypropylene?
a) 0.56 g/cm3
b) 0.90 g/cm3
c) 1.9 g/cm3
d) 0.68 g/cm3
Answer
Answer: b [Reason:] The density of polypropylene is about 0.90 g/cm3 and it also the lightest homo-polymer known.
3. What are the temperature and pressure conditions for the polymerization reaction of propylene?
a) 50-80 ᵒC and 5-25 atm
b) 50-80 ᵒC and 25-50 atm
c) 100-150 ᵒC and 5-25 atm
d) 100-150 ᵒC and 25-50 atm
Answer
Answer: a [Reason:] The polymerization reaction of propylene takes place at a temperature range of 50-80 ᵒC, generally at 60 ᵒC and at a low pressure range of 5-25 atm.
4. Which of the following is used as a catalyst in the polymerization of propylene?
a) MoO2
b) CrO3+Al2O3
c) Ni+Pt
d) TiCl4+Al(C2H5)3
Answer
Answer: d [Reason:] The polymerization of propylene take place by the Ziegler process in the presence of Ziegler Natta catalyst i.e. titanium halide and tri-alkyl aluminium.
5. Which of the solvent is used to check degree of isotacticity of polypropylene?
a) carbon tetra-cholirde
b) n-propane
c) n-hexane
d) n-heptane
Answer
Answer: d [Reason:] The degree of isotacticity or isotactic index of polypropylene is calculated as the percentage of the polymer that is insoluble in n-heptane.
6. Which of the following properties of polypropylene makes it inferior, when compared with polyethylene?
a) brittleness
b) tensile strength
c) clarity
d) stress cracking resitance
Answer
Answer: a [Reason:] Polypropylene becomes brittle when it is close to 0 ᵒC, and hence in this view it is inferior to polythelyene. Rest all other properties makes it superior to polyethylene as it has high tensile strength and clarity, and is occupied with less stress cracking problems.
7. Which among the following polymers is more prone to oxidation or aging?
a) LDPE
b) HDPE
c) Polypropylene
d) None of the mentioned
Answer
Answer: c [Reason:] Polypropylene is more prone to oxidation and aging than LDPE and HDPE, as it contains higher concentration of tertiary carbons.
8. Which of the following is not a reaction variable for polymerization of polypropylene?
a) molar ratio of catalyst composition
b) catalyst concentration
c) reaction temperature
d) none of the mentioned
Answer
Answer: d [Reason:] All the three variables, molar ratio of catalyst composition, catalyst concentration, and the reaction temperature are the reaction variable for the polymerization reaction of polypropylene.
9. Where among the following fields polypropylene cannot be used?
a) insulating cables and wires
b) home appliances
c) automobile appliances
d) furniture
Answer
Answer: a [Reason:] Polypropylene is used in the form of typical mouldings, which include components like automobile and home appliances, furniture and kitchenware, etc. and is not used for insulation purposes.
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