Multiple choice question for engineering
Set 1
1. Which of the following is not a reason for non-ideal kinetics of radical polymerization?
a) initiator-monomer complexation
b) unimolecular termination
c) degradative initiator transfer
d) none of the mentioned
Answer
Answer: d [Reason:] All the three mechanisms cause non-ideality and kinetic deviations in the radical polymerization.
2. Consider initiator-monomer complexation in polymerization reaction, and a straight line is plotted between [M]3/Rp2 and [M]. What is the value of quotient of slope and the intercept?
a) equilibrium rate constant of monomer complexation reaction, K
b) termination rate constant, kt
c) propagation rate constant, kp
d) initiator concentration
Answer
Answer: a [Reason:] The transformed rate equation, considering initiator monomer complexation, is given by-
[M]3/Rp2 = (kt/kp2 kd K[I0]) + (kt[M]/ kp2 kd [I0])
Thus, the slope of the straight line plotted is, kt/ kp2 kd [I0] and the intercept is kt/kp2 kd K[I0]. Therefore, the quotient is calculated as K.
3. What is the order of reaction with respect to initiator, considering exclusive case of unimolecular termination?
a) 1
b) 0
c) 2
d) 0.5
Answer
Answer: a [Reason:] For exclusive unimolecular termination,
Rt = kt1 [M∙]
Thus, the overall rate of polymerization is expressed as
Rp = kp/kt1 (2fkd) [I] [M]
Therefore, the initiator order is equal to 1.
4. Which of the following can restrict the bimolecular termination?
a) high monomer concentration
b) insolubility of polymer formed in monomer
c) presence of solvents, additives
d) none of the mentioned
Answer
Answer: b [Reason:] Bimolecular termination is restricted in heterogeneous polymerization, where the polymer formed is insoluble in the monomer solvent media and unimolecular termination shows prominence.
5. What are the initiator and monomer orders, in limiting case of exclusive primary radical termination?
a) 0, 2
b) 1, 2
c) 1, 1
d) 2, 0
Answer
Answer: a [Reason:] The rate of polymerization, taking into account exclusive primary radical termination mechanism, is given by
Rp = kp (ki/kprt)[M]2
where kprt is the rate constant for primary radical termination.
Thus, the initiator and monomer orders are 0 and 2, respectively.
6. What is the order of dependence of monomer concentration on Rp, in the exclusive case of degradative initiator transfer process?
a) 1
b) 0
c) 2
d) 0.5
Answer
Answer: a [Reason:] The overall rate maintains first order dependence on monomer concentration and the rate equation is given by-
Rp =( kp/kt’)(2fkd) [M].
7. How does the addition of solvents and additives, due to their abnormal effects, can affect the process of polymerization?
a) increase initiator efficiency
b) increase radical generation
c) enhance chain initiation rate
d) all of the mentioned
Answer
Answer: d [Reason:] The solvents, while behaving abnormally, sometimes can induce an increase in initiator efficiency or radical generation, which consequently increases the rate of chain initiation as well as polymerization.
8. What is the value of intercept of the line plotted between the terms (2kt/kp2)(Rp2/[I][M]2) and Rp/[M], when there is simultaneous occurrence of bimolecular termination and termination by degradative process?
a) 2fkd
b) fkd
c) kt’/kp
d) [I]
Answer
Answer: a [Reason:] For simultaneous occurrence of bimolecular termination and termination by degradative process, under steady-state condition, the equation is given by-
2kt[M∙]2 + kt’[I][M∙] = 2fkd [I].
On eliminating the radical concentration term, [M∙], we get
(2kt/kp2)(Rp2/[I][M]2) = 2fkd – (kt’/kp) Rp/[M] .
So, from the above equation, when straight line is plotted, it has a negative slope and the intercept value gives the value of 2fkd.
9. Viscosity of the polymerization medium has a great influence on the termination process. State true or false.
a) True
b) False
Answer
Answer: a [Reason:] Viscosity of the polymerization medium ofcourse has a influence on termination reaction, for termination being a diffusion based process. The solvent modification of termination reaction causes different kt values depending on the viscosity medium.
10. With the introduction of solvents in modifying the initiator species and affecting the degradative chain transfer, the value of parameter kp2/kt , changes with the solvent concentration. State true or false.
a) True
b) False
Answer
Answer: b [Reason:] The kinetic parameter kp2/kt practically remains unchanged over a whole range of dilution, when the solvents play an important role in modifying the initiator species and bring into effect noticeable degradative chain transfer.
Set 2
1. What is the special feature of the olefin metathesis and metathesis polymerization?
a) use of initiators
b) use of catalysts with high potential
c) use of solvents
d) none of the mentioned
Answer
Answer: b [Reason:] The special feature of this process is the use of catalyst with novel selectivity and high potential for effective chemical transformations for olefin metathesis.
2. What is the main driving force of the ring-opening metathesis polymerization reaction?
a) solvent concentration
b) relief of ring strain
c) catalyst activity
d) all of the mentioned
Answer
Answer: b [Reason:] The main driving force of the ROMP reaction is the relief of ring strain.
When the metal carbene attacks the double bond of the ring, it gives rise to highly strained intermediate. The ring then opens to give the beginning of the polymer.
3. Which of the following features are dependent on the solvent used in ring opening metathesis polymerization reaction?
a) rate of reaction
b) molecular weight
c) catalyst activity
d) all of the mentioned
Answer
Answer: d [Reason:] The solvent used plays an important role in the formation of carbene and thus affect the catalytic activity. Moreover by altering the solvent in the reaction, the rate of the reaction and the molecular weight of the polymer to be formed can be varied.
4. Which of the following functional group on the ring system poisoned the Grubb’s catalyst for the first time?
a) nitrile group
b) oxygenate groups
c) sulphate groups
d) hydrate groups
Answer
Answer: a [Reason:] Nitrile or amine groups poisoned the Grubb’s catalyst for the first time.
5. Which of the following substituent groups on the ring system can affect the Molybdenum or tungsten metathetic catalyst in ROMP?
a) oxygenate group
b) sulphate groups
c) amine groups
d) hydrate groups
Answer
Answer: a [Reason:] Molybdenum or Tungsten metathetic catalyst are affected by the oxygenate and nitrogenous groups attached to the ring in ROMP polymerization. The substituent groups can deleteriously react with the catalysts and affect its activity.
6. How does Norbornene epoxide affect the rate of ROMP reaction if RuCl3 and alcohol mixture is used as a catalyst?
a) increases
b) decreases
c) no change
d) cannot be determined
Answer
Answer: a [Reason:] This happens due to the production of metalloxacyclobutane complex, which directly gives the ruthenium trichloride carbene complex upon metathetic opening.
7. The formation of a regular polymer with regular double bonds contributes to the usefulness of the ROMP process. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] The ROMP process is useful because of the formation of a regular polymer with regular number of double bonds. Thus the final product is available for the partial or total hydrogenation to form more complex compounds.
Set 3
1. What is the characteristic feature of the gel effect in radical polymerization?
a) increase in kinetic rate
b) increase in molecular weight of product polymer
c) formation of highly viscous mass
d) all of the mentioned
Answer
Answer: d [Reason:] Gel or auto-acceleration effect is accompanied by increasing trend in reaction rate and molecular weight of polymer product, which results into the formation of highly viscous mass.
2. Where the gel effect is generally more evident in radical polymerization?
a) concentrated monomer
b) diluted monomer
c) independent of concentration
d) none of the mentioned
Answer
Answer: a [Reason:] The gel effect is more effectively manifested in undiluted monomers than diluted monomer, as non-ideal and unusual effect may be minimized. This effect can be lowered with progressive dilution.
3. Which of the following does auto-acceleration not depend upon?
a) initiator
b) monomer concentration
c) kinetic parameter (kp/kt0.5)
d) all of the mentioned
Answer
Answer: a [Reason:] The effect is independent of initiator, and so the change in fkd does not give any explanation for this observation.
4. What is the most convenient reason for auto-acceleration effect?
a) increase in kp
b) increase in kd
c) decrease in kt
d) increase in kt
Answer
Answer: c [Reason:] For Rp to rise, a sharp increase in the kinetic parameter (kp/kt0.5) is acceptable, which may arise due to increase in kp or decrease in kt. Since the values of kt are higher than the values of kp by a factor of 107-105 and due to termination hindrance, the decrease in the value of kt could be the most convenient reason.
5. Consider the consequences of rise in medium viscosity in gel effect.
I. There is hindrance to termination reaction.
II. The propagation reaction rises rapidly.
III. Reduction in diffusion of macro-radicals.
IV. Intrinsic reactivity of chain radicals is lowered.
Which of the following is true?
a) I, III
b) I,II &III
c) I, II, III & IV
d) I, II &IV
Answer
Answer: a [Reason:] There is no effective change in the propagation as it involves reaction between a macro-radical and a small monomer molecule. The intrinsic reactivity of the chain radicals remains same.
6. The auto-acceleration in may even lead to an explosion. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] The polymerization process associated with methyl acrylate, acrylic acid and acrylonitrile can accompany a huge rise in temperature and may even lead to an explosion.
7. Consider the following graph plotted between conversion and time taken, where benzoyl peroxide is used as an initiator.
Which of the following curve represents the lowest monomer concentration?
a) 1
b) 5
c) 4
d) 3
Answer
Answer: b [Reason:] The effect of auto-acceleration is eliminated with progressive dilution of monomer by a suitable solvent in the given graph. So curve 5 represents the most diluted monomer molecules.
8. What is the order of initiation reaction in self-initiated thermal polymerization?
a) 1
b) 2
c) 3
d) none of the mentioned
Answer
Answer: b [Reason:] Second order dependence of Rp on monomer concentration indicates that there is bimolecular initiation mechanism involved in spontaneous thermal polymerization.
9. How does the overall rate of spontaneous thermal polymerization vary, when the monomer concentration is doubled?
a) halved
b) doubled
c) quadrupled
d) remains constant
Answer
Answer: c [Reason:] The expression of related polymerization is given by-
Rp α [M]2
Thus, the rate is then increased by a factor of 4.
10. What kind of chain-initiating active centre is generated by bimolecular initiation mechanism of spontaneous thermal polymerization?
a) monoradical
b) biradical
c) ion
d) none of the mentioned
Answer
Answer: b [Reason:] The bimolecular initiation mechanism results in the formation of a biradical. For eg;
2CH2═CHX → ∙CH2(X)─CH2─(X)CH2∙.
11. The bimolecular biradical mechanism in spontaneous thermal polymerization is very appreciated for its successful attempts to induce polymerization by biradicals formed. State true or false.
a) true
b) false
Answer
Answer: b [Reason:] The bimolecular biradical mechanism in spontaneous thermal polymerization is criticized in the view of biradicals being vulnerable to cyclization and in view of unsuccessful attempts to induce polymerization by biradicals formed by decomposition of cyclic peroxy and azo compounds.
Set 4
1. Which of the following expressions correctly represents the number distribution function for a linear polycondensation reaction?(Here N0 and p are total number of initial monomer molecules and extent of reaction initially)
a) Nn=N0(1-p)2pn-1
b) Nn=N0(1-p)pn-1
c) Nn= N0pn-1
d) Nn</sub= N0n(1-p)2pn
Answer
Answer: a [Reason:] The probability Pn of formation of polymer molecule with n degree of polymerization is given by,
Pn=pn-1(1-p)
Where, Pn= Nn/N, and also N= N0(1-p), so the value on Nn comes out to be, Nn= N0(1-p)2pn-1.
2. Find the value of number average degree of polymerization for a mixture of polymers at 90% completion of reaction?
a) 0.1
b) 10
c) 100
d) 1.1
Answer
Answer: b [Reason:] The expression for Xn is given by,
Xn= 1/(1-p)
= 1/0.1
= 10
Thus, the value of number average degree of polymerization is 10.
3. What does the ratio of number to weight average degree of polymerization for a bifunctional system represent?
a) degree of polymerization
b) breadth of molecular size
c) extent of reaction
d) none of the mentioned
Answer
Answer: b [Reason:] The ratio, commonly, is used to represent the molecular size distribution, which is given by (1+p).
4. What are the values of number and weight average degree of polymerization for a bifunctional system at 95% completion of reaction?
a) 20, 39
b) 10,39
c) 2,3.9
d) 25,35
Answer
Answer: a [Reason:] The expressions for number and weight average degree of polymerization are given by,
Xn= 1/(1-p)
Xw= (1+p)/(1-p)
By putting the value of p, value of Xn and Xw can be calculated.
5. 80 moles of monomers react to prepare Nylon 12. After completion of 8 hrs, 4 moles of monomers are still left. What is the weight average molecular weight of polymer system?
a) 1263
b) 197
c) 3940
d) 7683
Answer
Answer: d [Reason:] The extent of reaction is-
p= 80-4/80 = 0.95
Thus, Xw= (1+p)/(1-p) = 39
Mw= Xw Mo= 197*39= 7683.
6. What are the number average molecular weights of Nylon 66 and Nylon 11, when the conversion is 90%?
a) 2260, 1830
b) 4294, 3477
c) 2586, 1830
d) 3477, 4200
Answer
Answer: a [Reason:] The value of Xn is given by,
Xn= 1/(1-p) = 1/(1-0.9)
= 10
Thus, for Nylon 66, Mn= 226*10=2260
For Nylon 11, Mn= 183*10= 1830
(226 and 183 are the molecular weights of the repeating units of polymer Nylon 66 and Nylon 11, respectively).
7. What is the maximum attainable degree of polymerization for 5% stoichiometric imbalance?
a) 52
b) 41
c) 63
d) 56
Answer
Answer: b [Reason:] For 5% impurity, the maximum attainable degree of polymerization will be,
Xn= [1+(100/105)]/[1-(100/105)]
Thus, Xn will be equal to 41.
8. Hydroxy caproic acids are used to polyester molecules. Due to improper purification of reactants, 2% of acid impurity was found. What is the number average degree of polymerization for 95% completion of reaction?
a) 2526
b) 2280
c) 1912
d) 1270
Answer
Answer: c [Reason:] For 2% acid impurity, r= 100/102= 0.98
Then, Xn is given by,
Xn= (1+r)/(1+r-2rp)
= 16.78
Thus, Mn= 114*16.78= 1912.
9. What is the probability of having tetramers in the preparation of Nylon 12, when 98% of functional groups have reacted?
a) 0.0189
b) 0.05
c) 0.256
d) 1
Answer
Answer: a [Reason:] The probability is given by,
Pn= pn-1(1-p)
= (0.98)3(0.02)
= 0.0189.
10. Which curve in the given figure possibly represents the highest value of conversion for bifunctional polycondensation?
a) 1
b) 2
c) 3
d) Cannot be determined
Answer
Answer: c [Reason:] Curve 3 possibly represents the highest conversion because the steepness of number fraction distribution curve falls with increasing value of p and the 3rd curve here is the most flattened one.
11. Consider the following graph plotted between weight fraction of molecules and degree of polymerization. What may be the possible value of p for the curve with highest peak?
a) 0.95
b) 0.99
c) 0.89
d) 0.92
Answer
Answer: c [Reason:] For a given value of p, Wn passes through a maximum and the maximum shifts to a higher value of n as the value of p increases. Therefore, the broadest curve represents highest p and the curve with highest peak represents the curve with lowest value of p.
12. What is the ratio of number to weight distribution function for a bifunctional system?
a) N0/n
b) N0
c) N
d) n/ N0
Answer
Answer: a [Reason:] For a bifunctional system,
Nn= N0(1-p)2pn-1
Wn= n(1-p)2pn-1
So, the ratio comes out to be N0/n.
Set 5
1. Which of the following monomer molecule does cumarone and indene resemble to?
a) ethylene
b) styrene
c) butadiene
d) cumene
Answer
Answer: b [Reason:] Cumarone and Indene are aromatic in nature and bear a vinylic kind of structure attached to aromatic ring, that’s why the closely resemble s to styrene.
2. Which catalyst is used in the resinification reaction of cumarone and indene?
a) nitric acid
b) sulphuric acid
c) stearic acid
d) boron trifluoride
Answer
Answer: b [Reason:] In the resinification reaction of cumarone and indene, they are polymerized in the crude naptha without separation using sulphuric acid as the ionic catalyst.
3. How should the temperature be kept to prevent premature gelation of of polyimides?
a) 30-40 C
b) 60-80 C
c) 55-65 C
d) 50-55 C
Answer
Answer: a [Reason:] The second stage reaction or premature gelation of polyimides can be prevented by using dry reactants in an anhydrous system free from pyromellitic acid and keeping the temperature low i.e. below 50 C.
4. Which of the following diamines is not used to prepare useful polyimides?
a) m-phenylene diamine
b) benzidine
c) m-benzylene diamine
d) 4,4-diaminodiphenylether
Answer
Answer: c [Reason:] The diamines that are used to make useful polyimides are m-phenylene diamine, benzidine and 4,4-diaminodiphenylether. M-benzylene diamine cannot be used to prepare polyimides.
5. Which of the following monomer pairs polymerize to give Perlon U?
a) hexamethylene diamine and adipic acid
b) hexamethylene diisocyanate and 1,4-butanediol
c) hexamethylene diamine and 1,4-butanediol
d) hexamethylene diisocyanate and adipic acid
Answer
Answer: b [Reason:] Perlon U is chemically known as polyurethane and is prepared by the rearrangement polymerization of hexamethylene diisocyanate and 1,4-butanediol by a step-growth mechanism.
6. Which of the following properties of polyurethane rubbers is incorrect as compared to other rubbers?
a) higher tensile strength
b) excellent abrasion resistance
c) excellent resistance to oxygen
d) excellent resistance to acids
Answer
Answer: d [Reason:] The polyurethane rubbers have higher tensile strength than any other rubber, excellent abrasion resistance and resistance to oxygen and ozone. However they are less resistant to acids and alkalies than other conventional rubbers.
7. Where is the polyurethane foams extensively used as?
a) adhesive
b) paint rollers
c) printing rollers
d) fabric coatings
Answer
Answer: b [Reason:] Polyurethane foams are extensively used as paint rollers, cushioning materials, soft backing or padding, etc. polyurethane rubbers are used as printing rollers and fabric coatings.
8. The ester interchange method is more favoured than direct phosgenation of bisphenol A for the production of polycarbonates. State true or false.
a) true
b) false
Answer
Answer: a [Reason:] Direct phosgenation reaction is better done in the presence of solvents and even diluted with certain other solvents. Thus, the ester interchange method is more favoured as it allows avoidance of handling of toxic and inflammable solvents and thus allowing avoidance of costs of solvents and solvent recovery.
9. Which of the following monomer pairs polymerize to give epoxy resin?
a) epichlorohydrin and bisphenol A
b) bisphenol A and diphenyl carbonate
c) bisphenol A and phosgene
d) none of the mentioned
Answer
Answer: a [Reason:] The polycondensation reaction between epichlorohydrin and bisphenol A gives epoxy resin as the product. The other two monomer pairs react and polymerize to give polycarbonates.
10. What is the use of epoxy resin from commercial point of view?
a) as strength adhesives
b) as cementing agents
c) cast objects and laminates
d) all of the mentioned
Answer
Answer: d [Reason:] The epoxy resins are especially used as high strength adhesives, cementing agents in building industry and also in glass fibre reinforced cast objects and laminates.
11. What is the common name of the polymer poly (ethylene terephthalate)?
a) dacron
b) technora
c) viton
d) nomex
Answer
Answer: a [Reason:] Poly (ethylene terephthalate) is commonly known as Dacron or Terylene.
12. What is the common or brand name of the polymer polyacrylonitrile?
a) mylar
b) orlon
c) technora
d) ultem
Answer
Answer:b [Reason:] The common brand name of poly acrylonitrile (PAN) is Orlon.
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