Solved Question Paper for Combined Test for Assistant Chemist in GSI, Foreman (Chemical) in DGAQA & Scientific Officer (Chemical) in National Test House conducted by UPSC

 81. For systems in which no termination is involved, as in the case of ‘Living Polymers’, an expression for the degree of polymerization can be found on the basis of:

1. The entire quantity of the initiator dissociation at the same time
2. All the anions formed by the dissociation initiative chain growth essentially simultaneously
3. All the anion compete equally for the monomer and the monomer is consumed more or less equally by all the anions
4. The entire quantity of the monomer dissociation at the same time

(a) 1, 3 and 4 only
(b) 1, 2 and 4 only
(c) 2, 3 and 4 only
(d) 1, 2 and 3 only

Answer: (d)

82. Consider the following statements regarding polymerization:
1. A high degree of polymerization can be achieved only at very low conversions and low temperatures
2. A high degree of polymerization can be achieved only at very high conversions
3. It is essential to start with exactly equimolar quantities of the reactants to achieve a high degree of polymerization
4. The presence of monofunctional impurities drastically reduces the degree of polymerization

Which of the above statements are correct?
(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 2, 3 and 4 only
(d) 1, 3 and 4 only

Answer: (c)

83. The average degree of polymerization D𝑝 can be correlated as:
1. D𝑝=2𝑣, when termination occurs by coupling
2. D𝑝=2𝑣/𝑁 , when termination occurs by coupling and disproportionation
3. D𝑝=𝑣, when termination occurs by disproportionation
4. D𝑝=𝑣/𝑁 , when termination occurs by disproportionation

Which of the above statements are correct?
(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 1, 3 and 4 only
(d) 2, 3 and 4 only

Answer: (c)

84. The kinetic chain length 𝑣 is:

Answer: (b)

85. The osmotic pressure (πœ‹) of a polymer solution is related to the number-average molecular weight of the polymer by the relation:

Answer: (a)

86. Dilatometric method is used to measure:
(a) Viscosity
(b) Atoms
(c) Expansion of coefficient of sample
(d) Accurate measurements of dimensional changes of polymeric samples

Answer: (c)

87. Which one of the following is used as the chain modifier in order to control the molecular weight in polymerization of butadiene?
(a) Zeigler-Natta catalyst
(b) Dodecyl mercaptan
(c) Polybutadienes
(d) Syndiotactic 1, 2-Polybutadiene

Answer: (b)

88. Natural rubber is obtained in the form of latex from rubber tree called:
(a) Acacia nilotica
(b) Bauhinia retusa
(c) Hevea brasiliensis
(d) Holarrhena floribunda

Answer: (c)

89. Ziegler-Natta catalysts are:
(a) Single-component organometallic compounds
(b) Initiators of polymer catalyst
(c) Special type of coordination catalyst
(d) Resonance-stabilized polymer catalyst

Answer: (c)

90. In Group Transfer Polymerization (GTP), which one of the following pair functions as group transfer catalyst?
(a) Ethyl trimethyl silyl acetate and trimethyl silyl cyanide
(b) 𝛼,𝛽-unsaturated esters and nitrites
(c) Ethyl methyl silyl cyanide and methyl ethyl silyl acetate
(d) Carbonamides silyl cyanide and ketene

Answer: (a)

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