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Multiple choice question for engineering

Set 1

1. Which of the following is not a characteristic of a cured urea resin?
a) hard and rigid
b) non-inflammable
c) excellent electrical insulation
d) impart colour and odour to food & drinks

View Answer

Answer: d [Reason:] The cured urea resins do not impart colour and odour to food and drinks with which they may come in contact. They are hard, rigid and non-inflammable but they char around 200 ᵒC. They exhibit excellent insulation properties.

2. Which of the following is used as a lubricant in the moulding powder from urea-formaldehyde resin?
a) zinc stearate
b) ammonium sulphamate
c) trimethyl phosphate
d) none of the mentioned

View Answer

Answer: a [Reason:] Metal stearate like zinc stearate, aluminium stearate, etc. (quantity about 1%) is used as a lubricant in the moulding powder.

3. Which of the following can be used to improve the shelf-life of moulding powders from urea-formaldehyde resin?
a) ammonium sulphamate
b) magnesium stearate
c) hexamine
d) ammonia

View Answer

Answer: c [Reason:] To improve the shelf life of moulding powders, it should be stored in cool place. Incorporation of a small amount of a stabilizer such as hexamine further improves shelf-life.

4. What is the ratio of urea o formaldehyde to produce useful resins?
a) 1:2
b) 2:1
c) 1:1
d) 1:3

View Answer

Answer: a [Reason:] Urea is potentially tetrafunctional and the use of 1.5 to 2 moles of formaldehyde for each mole of urea yields useful resins.

5. What is the pH requirement for the preparation of adhesive resins from urea formaldehyde resin?
a) 8
b) 7
c) 7.5
d) 9

View Answer

Answer: c [Reason:] The adhesive resins are prepared in the water solube form, stabilized by maintaining the pH at 7.5 and a solid content of nearly 50-70%.

6. Which of the following is commonly used as hardening agent for urea-formaldehyde resins?
a) ammonium chloride
b) sodium hydroxide
c) aluminium chloride
d) sodium carbonate

View Answer

Answer: a [Reason:] The resins are hardened under acidic conditions and ammonium chloride is used as most common hardening agent for resins which acts as acid donor.

7. What is the approximate reaction temperature in the formation of melamine, when cyanamide is heated to give dicyandiamide?
a) 300 C
b) 70 C
c) 100 C
d) 180 C

View Answer

Answer: b [Reason:] Dicyandiamide is produced by heating cyanamide at a temperature of about 70-80 C.

8. What is the initial molar ratio for melamine to formaldehyde in commercial resinification reaction?
a) 1:3
b) 1:2
c) 3:1
d) 2:1

View Answer

Answer: a [Reason:] An initial molar ratio of 1:3 for melamine to formaldehyde is used in commercial resinification reactions.

9. What are the temperature and pressure conditions for the compression moulding of m-f resin?
a) 200-250 C and 1000-3000 psi
b) 150-170 C and 2000-8000 psi
c) 150-170 C and 1000-3000 psi
d) 200-250 C and 2000-8000 psi

View Answer

Answer: b [Reason:] The temperatures in the range of 150-170 C and pressure of the order 2000-8000 psi are employed for compression moulding of m-f resins.

10. What is the extensive use of melamine-formaldehyde resins?
a) decorative laminates
b) stove enamels
c) air-drying lacquers
d) art and jewellery

View Answer

Answer: a [Reason:] The exceptional hardness, solvent resistance and heat stability qualities of m-f resin make it suitable to be used as decorative laminates.

11. Which catalyst is used in the production of electrical grade laminates from m-f resin?
a) triethanolamine
b) sodium carbonate
c) sodium hydroxide
d) ethanamine

View Answer

Answer: a [Reason:] The electrical grade laminates are produced by using triethanolamine as condensation catalyst rather than sodium carbonate as catalyst. They are usually made by impregnationg electrical-grade glass cloth with the triethanolamine catalyzed resin.

Set 2

1. How the termination in anionic polymerization most probably does take place?
a) unimolecular termination
b) bimolecular
c) termination by solvent transfer
d) all of the mentioned

View Answer

Answer: c [Reason:] The termination reaction in anionic polymerization most probably takes place by the chain transfer involving solvent or some other additive used such as water, alcohol, etc.

2. Which of the following monomer has the least reactivity towards anionic polymerization?
a) acrylonitrile
b) methyl metharylate
c) butadiene
d) methacrylonitrile

View Answer

Answer: c [Reason:] According to the reactivity order given by Mayo and Walling, Acrylonitrile>Methacrylonitrile>Methyl methacrylate>butadiene This order is decided on the basis of the electronegativity of the electron-withdrawing substituent groups.

3. Which of the following nature of solvent can inhibit the growth of polymer in anionic polymerization?
a) acidic
b) basic
c) neutral
d) none of the mentioned

View Answer

Answer: a [Reason:] Acidic solvents or additives inhibit the growth in anionic polymerization.

4. What kind of substituent groups should be attached to the monomer, readily undergoing anionic polymerization?
a) electron accepting
b) electron releasing
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: a [Reason:] The monomers with electron accepting substituent groups like nitrile, carboxyl, ester groups, etc. are readily susceptible to anionic polymerization as the it enables easy carbanion formation.

5. The ease of anionic polymerization is dependent only on the catalyst system used for a given monomer. State true or false.
a) true
b) false

View Answer

Answer: b [Reason:] The ease of anionic polymerization is dependent not only on the catalyst system for a given monomer, but also on the structure of the monomer for a given catalyst.

6. Which of the following can assist as a catalyst in anionic polymerization?
a) Sulphuric acid
b) Boron trifluoride
c) grignard reagent
d) all of the mentioned

View Answer

Answer: c [Reason:] The basic compounds like amides, aryls, alkoxides and Grignard reagents (R-MgX) are used as catalysts for anionic polymerization.

7. What does the effectiveness of the catalyst in the initiation process of anionic polymerization depend on?
a) acidity of the monomer
b) basicity of the catalyst
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: c [Reason:] The effectiveness of the catalyst in the initiation process of anionic polymerization depends on its basicity as well as the acidity of monomer.

8. Styrene is polymerized using amide catalyst in liquid ammonia, anionically. How will the rate of reaction change, if the monomer concentration is doubled (keeping rest other things constant)?
a) doubled
b) halved
c) quadrupled
d) No change

View Answer

Answer: c [Reason:] According to the rate expression for overall rate Rp α [M]2 So the rate is quadrupled, if the monomer concentration is doubled.

9. Which of the following monomers is more prone to form low-molecular weight polymer when polymerized in liquid ammonia?
a) acrylonitrile
b) metha acrylonitirile
c) styrene
d) methyl methacrylonitrile

View Answer

Answer: c [Reason:] Styrene contains the phenyl group which is less electronegative than the nitrile group (-CN) attached to the other three monomers, so it is more susceptible to proton transfer from ammonia. And transfer reactions generally yield low-molecular weight polymers.

10. How is the degree of polymerization affected with the increase in concentration of both monomer and liquid ammonia, when a monomer is polymerized anionically in liquid ammonia?
a) increases
b) decreases
c) no change
d) cannot be determined

View Answer

Answer: d [Reason:] According to the expression for degree of polymerization, Xn α [M]/[NH3] Since the degree of increase in the concentration of both monomer and liquid ammonia is not known, we cannot determine that whether the degree of polymerization will increase or decrease.

Set 3

1. Which of the following polymerization mechanism can polymerize the styrene monomer?
a) cationic polymerization
b) radical polymerization
c) anionic polymerization
d) all of the mentioned

View Answer

Answer: d [Reason:] Styrene is capable of polymerizing by radical as well as cationic and anionic mechanisms. It is placed at a low position in each series of reactivity.

2. Which of the following type of termination is not possible in ionic polymerization?
a) bimolecular termination
b) unimolecular termination
c) termination through transfer to monomer or solvent
d) none of the mentioned

View Answer

Answer: a [Reason:] Bimolecular termination is not feasible in the ionic polymerization, as like charges repel each other and cannot come close enough to interact with each other and annihilate together.

3. Which of the following nature of solvent or additives can inhibit the growth in cationic polymerization?
a) basic
b) acidic
c) neutral
d) none of the mentioned

View Answer

Answer: a [Reason:] Basic solvents or additives can inhibit the growth of polymer in cationic polymerization.

4. Which of the following monomer has highest reactivity towards cationic polymerization?
a) isobutylene
b) isoprene
c) vinyl ethers
d) styrene

View Answer

Answer: c [Reason:] The reactivity order for cationic polymerization proposed by Mayo and Walling states- Vinyl ethers>isobutylene>isoprene>styrene.

5. What kind of substituent groups should be attached to the monomer, readily undergoing cationic polymerization?
a) electron accepting
b) electron releasing
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: b [Reason:] The monomers with electron releasing substituent groups like alkoxy, phenyl, aryl-alkyl, etc. are readily susceptible to cationic polymerization as the it enables easy carbonium formation.

6. How does degree of polymerization affected with increase in temperature of cationic polymerization reaction?
a) increases
b) decreases
c) no change
d) cannot be determined

View Answer

Answer: b [Reason:] Cationic polymerization generally occurs around -100ᵒC temperature. So, the rate and degree of polymerization drops sharply with rise in the temperature.

7. How is the rate of polymerization dependent on the concentration of catalyst in cationic polymerization?
a) proportional to first power
b) proportional to half power
c) proportional to second power
d) no dependence

View Answer

Answer: a [Reason:] The rate of cationic polymerization is given by- Rp= (kikp/kt)[C][M]2 Thus, Rp is proportional to the first power of catalyst concentration.

8. What is true about the degree of cationic polymerization when termination occurs by monomer transfer?
a) constant
b) proportional to monomer concentration
c) proportional to catalyst concentration
d) proportional to square of monomer concentration

View Answer

Answer: a [Reason:] The degree of polymerization for transfer reaction is given is a constant which is given by- Xn= kp[M+][M]/ktr[M+][M] Xn= kp/ktr Where kp and ktr are propagation and termination constants.

9. What does the binding energy between the propagating ion and the gegen ion depend on?
a) nature of reaction media
b) nature of gegen ion
c) temperature of reaction
d) all of the mentioned

View Answer

Answer: d [Reason:] The binding energy between the propagating ion and the gegen ion is dependent on the nature of the reaction media and the gegen ion and on the temperature of the reaction.

10. What is the range of activation energy of overall polymerization of cationic polymerization?
a) -10 to +10 kcal/mol
b) -100 to +100 kcal/mol
c) -500 to +500 kcal/mol
d) -25 to +25 kcal/mol

View Answer

Answer: a [Reason:] The activation energy for the overall rate is given by [(Ei+Ep)-Et] and it ranges between -10 to +10 kcal/mol.

11. The magnitude of the negative activation energy for degree of polymerization is higher for true termination than that for the termination by transfer reactions. State true or false.
a) true
b) false

View Answer

Answer: b [Reason:] The activation energy for degree of polymerization is given by (Ep-Et) and Et>Ep giving always a negative value. Since Etr (for transfer reaction) is generally greater than Et (for true termination), the magnitude of negative activation energy is higher for the termination by transfer reactions than for the true termination.

12. BF3 is ineffective to induce cationic polymerization in isobutylene when the reactants are moisture free. State true or false.
a) true
b) false

View Answer

Answer: a [Reason:] BF3 is very effective in the presence of traces of moisture as a co-catalyst as it reacts with traces of moisture to form a complex (BF3∙H2O) which can readily induce polymerization.

13. How is the rate of cationic polymerization reaction affected with the increase in the dielectric constant of the reaction medium?
a) increase
b) decreases
c) may increase or decrease
d) no effect

View Answer

Answer: a [Reason:] The increase in dielectric constant of reaction medium increases the initiation rate constant, ki by decreasing the energy required for charge separation and simultaneously, it decreases the termination constant, kt by increasing the energy required for arrangement or combination of ion pair. Since, Rp is directly proportional to the ratio ki/kt, an increase in the dielectric constant of reaction medium will increase the rate of reaction.

Set 4

1. Which of the following area of application restricts the use of cellulose nitrate?
a) photographic films
b) lacquor coatings
c) tool handles
d) printing inks

View Answer

Answer: a [Reason:] Due to high inflammability and poor chemical and solvent resistance of cellulose nitrate, the use of cellulose nitrate in many areas of application has been considered no suitable. Those areas include photographic films, machine guards, toys, etc. Presently, it finds use in lacquor coatings and printing inks, tool handles, etc.

2. What is the role of H2SO4 in the preparation of cellulose nitrate?
a) catalyst
b) condensing agent
c) plasticizer
d) swelling agent

View Answer

Answer: b [Reason:] H2SO4 is used as a condensing agent. A very low content of water tends to produce high degree of nitration and H2SO4 provides that service.

3. What should be the content of N2 in commercial cellulose nitrate used for plastic and coating purposes?
a) 10.9-12.2%
b) 13.5-14%
c) 8.9-9.2%
d) 16-18%

View Answer

Answer: a [Reason:] Commercial cellulose nitrate used for plastic and coating applications have N2 content in the range of 10.9-12.2% whereas nitrates with N2 content greater than 12.5 are used for explosives.

4. Which of the following acts as a swelling agent for the cellulose in preparation of cellulose acetate?
a) acetic anhydride
b) acetic acid
c) sulphuric acid
d) alkyl chloride

View Answer

Answer: b [Reason:] Acetic acid acts as a swelling agent for the cellulose and the pretreatment by it, makes cellulose swell whereby it makes accessible to acetic anhydride for acetylation.

5. Which of the following type of cellulose acetate is soluble in chloroform?
a) primary cellulose acetate
b) secondary cellulose acetate
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: a [Reason:] The primary acetate is soluble in the chlorinated hydrocarbons like chloroform and trichloro ethane while secondary acetate is insoluble in chloroform.

6. Which of the following cellulose ethers is used as viscosity modifiers in aqueous suspensions and emulsions?
a) ethyl cellulose
b) methyl cellulose
c) sodium carboxymethyl cellulose
d) propyl cellulose

View Answer

Answer: c [Reason:] Sodium carboxymethyl cellulose of DS in the range of 0.5-1.0 is water soluble and is used in synthetic detergents and as stabilizers and viscosity modifiers in aqueous suspensions and emulsions. Ethyl cellulose is used in hot melt strippable coating formulations and surface coating formulations while methyl cellulose is used as a thickening agent and an emulsifying agent.

7. Which solvent is used for reaction with soda cellulose in the production of regenerated cellulose?
a) carbon disulphide
b) carbon tetrachloride
c) toluene
d) none of the mentioned

View Answer

Answer: a [Reason:] Soda cellulose is transformed into sodium cellulose xanthate by reacting it with CS2 i.e. carbon disulphide. The xanthate formed is soluble in dilute aqueous alkali, which on acidification decomposes; the xanthate structure is broken and cellulose is regenerated.

8. What is the film called, that is formed by the viscose solution of sodium cellulose xanthate?
a) celluloid
b) cellophane
c) cellulite
d) viscose rayon

View Answer

Answer: b [Reason:] The film formed by the viscose solution is known as cellophane and the fibre formed is called viscose rayon. Celluloid is a camphor plasticized product.

9. Cellulose acetate-butyrate is more suitable than cellulose acetate for producing movie films. State true or false.
a) true
b) false

View Answer

Answer: a [Reason:] Cellulose acetate-butyrate is more suitable for producing movie films due its excellent appearance and clarity, toughness and ease of mould ability over cellulose acetate.

Set 5

1. What does the effect of chain transfer on Rp depend on?
a) re-initiation rate constant, ki
b) monomer concentration
c) ki/kp
d) none of the mentioned

View Answer

Answer: c [Reason:] The effect of chain transfer on Rp depends upon the value of re-initiation constant relative to the value of propagation constant. If ki<< kp, then chain transfer agent would play the role of an inhibitor or retarder and Rp would be adversely affected.

2. How is the value of average degree of polymerization defined, considering the chain transfer mechanism?
a) ratio of overall rate of polymerization to total rate of production of pairs of chain ends
b) ratio of total rate of production of chain ends to overall rate of polymerization
c) ratio of overall rate of polymerization to rate of formation of pairs of chain ends by chain transfer
d) ratio of rate of formation of pairs of chain ends by chain transfer to overall rate of polymerization

View Answer

Answer: a [Reason:] The average degree of polymerization is redefined from the kinetic view point as the ratio of overall rate of polymerization to total rate of production of pairs of chain ends.

3. What is the value of chain transfer constant for a transfer agent?
a) rate constant for chain transfer reaction, ktr
b) product of ktr and kp
c) ratio of ktr to kp
d) none of the mentioned

View Answer

Answer: c [Reason:] The chain transfer constant C is defined as the ratio of rate constant, ktr for chain transfer reaction to the propagation rate constant.

4. What is the value of intercept, when (1/Xn) is plotted against Rp, if only monomer transfer has a significant occurence?
a) 0
b) CM
c) CI
d) [I] 

View Answer

Answer: b [Reason:] In the absence of any solvent in polymerization system, the expression for (1/Xn) is arranged as- 1/Xn = [(y+2)/(y+1)](kt/kp2)(Rp/[M]2) + CM + CI [I]/[M] When only monomer transfer takes place, the intercept on 1/Xn axis gives a measure of monomer transfer constant, CM.

5. What is the value of intercept and slope of the straight line, when the term [1/Xn– [(y+2)/(y+1)](kt/kp2)(Rp/[M]2)] is plotted against the ratio [I]/[M], when both monomer and initiator transfer are considered?
a) CM, CI
b) CI, CM
c) 0, CI
d) none of the mentioned

View Answer

Answer: a [Reason:] The plot of [1/Xn – [(y+2)/(y+1)](kt/kp2)(Rp/[M]2)] vs [I]/[M] gives a straight line, whose intercept gives a direct measure of CM and slope gives the value of initiator transfer constant, CI.

6. How does the value of solvent transfer constant, CS vary in the solvents with increasing substitution at the α-carbon?
a) increases
b) decreases
c) constant
d) none of the mentioned

View Answer

Answer: a [Reason:] The reactivity increases with the increasing substitution at the α-carbon, which leads to increasing values of CS in the order benzene < toluene < ethyl benzene < isopropyl benzene.

7. Which of the following solvents is not useful for controlling the degree of polymerization?
a) carbon tetra-bromide
b) pentaphenyl ethane
c) t-butyl mercaptan
d) toluene

View Answer

Answer: d [Reason:] The other three solvents exhibit high chain transfer activity; they surpass styrene in reactivity towards chain radical and have CS values greater than unity. Toluene, on the other hand, has a very low CS value to control the degree of polymerization.

8. What is the slope of the linear plot of log [S] v/s log [M] in significant solvent transfer mechanism?
a) CM
b) CS
c) ktr,S
d) CI

View Answer

Answer: b [Reason:] The ratio of rate of consumption of the transfer agent and the rate of consumption of monomer can be written as, (d[S]/dt)/(d[M]/dt) = ktr,S[M]/kp[S] = CS [M]/[S] d log[M]/d log [S] = CS Hence for this system, the linear plot of log [M] against log [S] renders the slope of solvent transfer constant, CS.

9. What is the effect of polymer transfer on the polymer product formed by radical polymerization?
a) becomes less crystallizable
b) becomes mechanically weak
c) becomes less resistant to foreign agents
d) all of the mentioned

View Answer

Answer:d [Reason:] The polymer transfer leads to the chain branching which makes it less crystalizable, weak in mechanical properties and less resistant to heat, solvents and chemicals.

10. For polymerization of vinyl acetate with hydrogen peroxide at 60ᵒC, the reciprocal of number average degree of polymerization is given by,
1/Xn = 1.75*10-4 + 14.0Rp + 5.4*104Rp2
What is the value of monomer transfer constant?
a) 1.75*10-4
b) 0.875*10-4
c) 5.4*104
d) 14

View Answer

Answer: a [Reason:] According to the expression for reciprocal of average degree of polymerization, we have 1/Xn = CM + (kt/kp2)(Rp/[M]2) + CI(kt/kp2 fkd)(Rp2/[M]3) Comparing the given equation with this one, we get CM as 1.75* 10-4.

11. Consider the expression for reciprocal of average degree of polymerization, when styrene is polymerized with t-butyl hydroperoxide at 60ᵒC-
1/Xn = 0.6*10-4+10.0Rp+1.73*104 Rp2
Calculate the value of initiator transfer constant, if the monomer concentration is 8.35 mol/l and the value of the term kp2 fkd/kt= 3.29*10-9.
a) 0.035
b) 0.07
c) 0.063
d) 0.0175

View Answer

Answer: a [Reason:] According to the expression for reciprocal of average degree of polymerization, we have 1/Xn = CM + (kt/kp2)(Rp/[M]2) + CI(kt/kp2 fkd)(Rp2/[M]3) Comparing the given equation, CI(kt/kp2 fkd)(Rp2/[M]3) = 1.73*104 Rp2 CI = 1.73*104 * 3.29*10-9*(8.35)3 CI = 0.035.

12. The transfer constant to the solvent for polymerization of of styrene in toluene at 60ᵒC is 0.125*10-5. How much dilution is required to decrease the molecular weight by 4 times when 1/Xn0 is 3.5*10-4?
a) 75
b) 42
c) 84
d) 7

View Answer

Answer: c [Reason:] To decrease molecular weight by 4 times, 1/Xn becomes 4/Xn0, 4/Xn0 = 1/Xn0 + CI [S]/[M] Substituting the values, [S]/[M] = 84. Thus, dilution factor is 84.

13. The molecular weight of the polymer, when styrene is polymerized at 60ᵒC, is halved by diluting it with ethyl benzene. What is the value of transfer constant to the solvent, if the dilution factor is 7 and the term 1/Xn0 is 4.8*10-4?
a) 0.335
b) 0.68
c) 1.5
d) 0.82

View Answer

Answer: b [Reason:] We have the expression for solvent transfer, 1/Xn = 1/Xn0 + CI [S]/[M] When molecular weight is halved, 1/Xn becomes 2/Xn0, then substituting the values and [S]/[M]= 7, we get CI as 0.68.