GATE XE topic:engineering-sciences PYQs & Answers — Page 50

Questions 491–500 of 1772. Imported answers require independent review unless marked reviewed.

The propagation step of a free radical copolymerization is represented by the following possible reaction steps:

P1:

, rate constant =

P2:

, rate constant =

P3:

, rate constant =

P4:

, rate constant =

where,

and

are two monomers and

and

are the active radicals of

and

, respectively.

(

) represents the rate constant of each step as shown above.

If the reactivity ratios of

and

are expressed as:

and

, respectively, and feed mole ratio,

is expressed as

(where,

and

are the concentrations of

and

, respectively), the probability of the reaction P2 is ______.

Your answerChoose one option.

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Match the following additives to their respective functions for poly(vinyl chloride) compounding.

Additive	Function
P. Dibutyl tin maleate	1. Lubricant
Q. Epoxided soybean oil	2. Extender
R. Chlorinated paraffin wax	3. Heat stabilizer
S. Calcium stearate	4. Plasticizer

Your answerChoose one option.

P-3; Q-4; R-2; S-1

P-2; Q-4; R-1; S-3

P-3; Q-2; R-1; S-4

P-4; Q-2; R-1; S-3

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Match the following properties with their respective units.

Property	Unit
P. Notched Izod impact strength	1. Pa s
Q. Flexural strength	2. J m
R. Dielectric strength	3. MPa
S. Complex viscosity	4. kV cm

Your answerChoose one option.

P-1; Q-2; R-3; S-4

P-2; Q-1; R-3; S-4

P-2; Q-3; R-4; S-1

P-3; Q-1; R-2; S-4

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Melt flow index (

) of a polymer depends on its molecular weight (

) and melt viscosity (

). Select the correct relation(s) from the following.

Your answerSelect all correct options. You can choose more than one.

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Biaxially oriented poly(propylene) exhibits high clarity because layering of the crystalline structures

Your answerSelect all correct options. You can choose more than one.

decreases the variation in refractive index across the film thickness

decreases the amount of light scattering

increases the variation in refractive index across the film thickness

increases the amount of light scattering

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If a given poly(ethylene) sample with specific volume,

shows: specific volume of the crystalline fraction,

and specific volume of the amorphous fraction,

, then the % crystallinity (based on mass fraction) of the poly(ethylene) sample is ______ % (rounded off to the nearest integer).

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The glass transition temperature (

) of poly(2,6-dimethyl-p-phenylene oxide) (PPO) is 206 °C and the

of poly(styrene) (PS) is 90 °C. The

of a 50/50 (wt/wt) miscible blend of PPO/PS is ______ °C (rounded off to the nearest integer).

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A unidirectional composite is prepared using 70% by volume of epoxy matrix and 30% by volume of carbon fibre. The elastic modulus of the epoxy matrix is 3.5 GPa and the elastic modulus of the carbon fibre is 350 GPa. The longitudinal elastic modulus of the composite is ______ GPa (rounded off to the nearest integer).

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Polyamide 66 is prepared by the condensation polymerization of 0.08 mol of hexamethylene diamine with 0.08 mol of adipic acid. At the end of the polymerization reaction, the reaction product contained 0.002 mol of unreacted carboxylic acid groups. The molecular weight of the repeat unit of polyamide 66 is 226 g mol

. The number-average molecular weight (

) of the polyamide 66 in the reaction product is ______ g mol

(rounded off to the nearest integer).

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A monodisperse polymer sample of molecular weight 10,000 g mol

is mixed with another monodisperse sample of the same polymer of molecular weight 50,000 g mol

. The total mass of the mixture is 1,000 g and the total number of moles of the polymer in the mixture is 0.04 mol. The weight-average molecular weight (

) of the polymer mixture is ______ g mol

(rounded off to the nearest integer).

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GATE XE topic:engineering-sciences PYQs

Question 119

Question 120

Question 121

Question 122

Question 123

Question 124

Question 125

Question 126

Question 127

Question 128