NSEC 2020 Question Paper

NSEC 2020 - Question 1

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Reaction of ammonia with diborane gives an ionic product $$\text{B}_2\text{H}_6 \cdot 2\text{NH}_3$$. The hybridization of boron in the cation and anion of this product are respectively

A

$$sp^3$$ in both

B

$$sp^3$$ and $$sp^2$$

C

$$sp^2$$ and $$sp^3$$

D

$$sp^2$$ in both

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NSEC 2020 - Question 2

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A sequence of reactions of phosphorus $$\text{P}_4$$ is given below. The correct set of products Q, R, S and T among the following is

A

$$\text{Q} = \text{PCl}_3$$, $$\text{R} = \text{POCl}_3$$, $$\text{S} = \text{P}_2\text{O}_3$$, $$\text{T} = \text{H}_3\text{PO}_3$$

B

$$\text{Q} = \text{PCl}_5$$, $$\text{R} = \text{P}_2\text{O}_5$$, $$\text{S} = \text{P}_4\text{O}_6$$, $$\text{T} = \text{H}_3\text{PO}_3$$

C

$$\text{Q} = \text{PCl}_3$$, $$\text{R} = \text{POCl}_3$$, $$\text{S} = \text{P}_4\text{O}_{10}$$, $$\text{T} = \text{H}_3\text{PO}_4$$

D

$$\text{Q} = \text{PCl}_5$$, $$\text{R} = \text{P}_4\text{O}_{10}$$, $$\text{S} = \text{P}_4\text{O}_{10}$$, $$\text{T} = \text{H}_3\text{PO}_4$$

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NSEC 2020 - Question 3

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In the gaseous state of $$\text{Fe(CO)}_5$$, the d orbital that would participate in hybridization is

A

$$d_{x^2 - y^2}$$

B

$$d_{z^2}$$

C

$$d_{xz}$$

D

any one of the d orbitals

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NSEC 2020 - Question 4

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Among the following, the correct statements about p block elements are
I. The valence shell electronic configuration of all of them is $$ns^2 np^{1-6}$$
II. Only in p block, metals, nonmetals and metalloids are present
III. Halogens have the lowest negative electron gain enthalpy in the respective periods
IV. Noble gases have no tendency to accept an electron and hence they have large negative values of electron gain enthalpy

A

I, IV

B

II, III

C

IV only

D

II only

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NSEC 2020 - Question 5

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A chemical reaction is carried out at two different temperatures $$T_1$$ and $$T_2$$ with $$T_2 > T_1$$, and also with and without a catalyst. The statement that is correct among the following is

A

Lowering in the activation energy of the reaction due to catalyst would be higher at $$T_2$$ than at $$T_1$$

B

Lowering in the activation energy of the reaction due to catalyst would be higher at $$T_1$$ than at $$T_2$$

C

The factor by which the rate of the reaction is increased by the catalyst would be lower at $$T_2$$ than at $$T_1$$

D

The factor by which the rate of the reaction is increased by the catalyst would be higher at $$T_2$$ than at $$T_1$$

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NSEC 2020 - Question 6

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The product P in the following sequence of reactions is

A

A

B

B

C

C

D

D

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NSEC 2020 - Question 7

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Among the following, maximum number of resonance structures is possible for

A

$$\text{PO}_4^{-3}$$

B

$$\text{SO}_4^{-2}$$

C

$$\text{CO}_3^{-2}$$

D

$$\text{MnO}_4^-$$

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NSEC 2020 - Question 8

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A mixture of sodium (Na) and potassium (K) metals weighing 32 g was reacted with water and the solution obtained could be neutralized with 517.3 mL of 1.0 M $$\text{H}_2\text{SO}_4$$ (aq). The mass of sodium that was present in the mixture is

A

20 g

B

16 g

C

10 g

D

12 g

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NSEC 2020 - Question 9

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The mass ratio of steam and hydrogen is found to be $$1 \colon 1.5$$ at equilibrium in the reaction $$3\text{Fe}(s) + 4\text{H}_2\text{O}(g) \rightleftharpoons \text{Fe}_3\text{O}_4(s) + 4\text{H}_2(g)$$. The value of the equilibrium constant $$K_c$$ of the above reaction is

A

$$3.0 \times 10^{-5}$$

B

$$3.3 \times 10^4$$

C

$$3.3 \times 10^6$$

D

$$1.3 \times 10^3$$

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NSEC 2020 - Question 10

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Two students did a set of experiments on ketones X and Y independently and obtained the following results.

The ketones X and Y are respectively

A

2-ethylcyclobutanone and 3-ethylcyclobutanone

B

2-methylcyclopentanone and 3-methylcyclopentanone

C

3-methylcyclopentanone and 2-methylcyclopentanone

D

3-methyl-4-penten-2-one and 4-methyl-1-penten-3-one

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NSEC 2020 - Question 11

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Glycine $$\text{C}_2\text{H}_5\text{O}_2\text{N}$$ is the simplest of amino acids. Molecular formula of the linear oligomer synthesized by linking ten glycine molecules together via a condensation reaction would be

A

$$\text{C}_{20}\text{H}_{32}\text{O}_{11}\text{N}_{10}$$

B

$$\text{C}_{20}\text{H}_{68}\text{O}_{29}\text{N}_{10}$$

C

$$\text{C}_{20}\text{H}_{40}\text{O}_{10}\text{N}_{10}$$

D

$$\text{C}_{20}\text{H}_{50}\text{O}_{20}\text{N}_{10}$$

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NSEC 2020 - Question 12

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If $$\text{Ni}^{2+}$$ is replaced by $$\text{Pt}^{2+}$$ in the complex ion $$[\text{NiCl}_2\text{Br}_2]^{2-}$$, which of the following would change? I. Magnetic moment II. Geometry III. Geometrical isomerism IV. Optical isomerism

A

I, II, III

B

II, III

C

I, II

D

II, III, IV

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NSEC 2020 - Question 13

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An inorganic compound X of an alkali metal on heating gives a reddish-brown gas Y and a binary solid Z. This solid is less soluble in water and its solution is basic. X does not give a positive silver nitrate test. X can be identified as

A

$$\text{KIO}_3$$

B

$$\text{LiNO}_3$$

C

$$\text{NaNO}_3$$

D

$$\text{KNO}_2$$

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NSEC 2020 - Question 14

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The qualitative plots given represent the yield of the product [XY] at equilibrium in the reaction $$\text{X}(g) + \text{Y}(g) \rightleftharpoons \text{XY}(g)$$ as a function of temperature, at total pressures $$P_1$$ and $$P_2$$. The reaction is

A

endothermic and $$P_1 < P_2$$

B

endothermic and $$P_2 < P_1$$

C

exothermic and $$P_1 > P_2$$

D

exothermic and $$P_2 > P_1$$

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NSEC 2020 - Question 15

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When 6.8 g of $$\text{AgNO}_3$$ completely reacts with $$\text{H}_3\text{PO}_2$$, the metallic silver produced in g and the $$\text{H}_3\text{PO}_2$$ consumed in mole are respectively

A

4.32 and 0.1

B

1.08 and 0.01

C

4.32 and 0.01

D

2.16 and 0.01

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NSEC 2020 - Question 16

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Lovastatin, a drug used to reduce the risk of cardio vascular diseases, has the following structure.

The number of stereogenic centers present in lovastatin is

A

8

B

3

C

4

D

6

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NSEC 2020 - Question 17

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Among the following sets, the one in which all the molecules are non polar is

A

$$\text{XeF}_4$$, $$\text{XeO}_3$$, $$\text{XeO}_4$$

B

$$\text{XeF}_2$$, $$\text{XeO}_4$$, $$\text{XeOF}_4$$

C

$$\text{XeF}_2$$, $$\text{XeF}_4$$, $$\text{XeO}_4$$

D

$$\text{XeF}_2$$, $$\text{XeO}_3$$, $$\text{XeOF}_4$$

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NSEC 2020 - Question 18

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Gas phase reactions (i) and (ii) are of first and second order respectively, where
(i) is $$2\text{N}_2\text{O}_5 \rightarrow 4\text{NO}_2 + \text{O}_2$$ and
(ii) is $$2\text{NO} + \text{O}_2 \rightarrow 2\text{NO}_2$$.
Under certain conditions the rate constants $$k_1$$ and $$k_2$$ of (i) and (ii) respectively have the same numerical value when the concentrations of the reactants are expressed in mol $$\text{dm}^{-3}$$. If the concentrations are expressed in mol $$\text{mL}^{-1}$$, the correct relationship between $$k_1$$ and $$k_2$$ is

A

$$k_2 \times 10^{-3} = k_1$$

B

$$k_2 \times 10^3 = k_1$$

C

$$k_1 = k_2$$

D

$$k_1 \times 10^6 = k_2$$

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NSEC 2020 - Question 19

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The correct sequence of reactions to get Q as the only product from P is

A

(i) $$\text{H}_2$$ and Pt catalyst (ii) $$\text{C}_2\text{H}_5\text{Cl}$$ and $$\text{AlCl}_3$$

B

(i) Mg in ether (ii) aqueous alcohol (iii) $$\text{C}_2\text{H}_5\text{Cl}$$ and $$\text{AlCl}_3$$

C

(i) Mg in ether (ii) $$\text{C}_2\text{H}_5\text{Cl}$$ and $$\text{AlCl}_3$$

D

(i) $$\text{C}_2\text{H}_5\text{Cl}$$ and $$\text{AlCl}_3$$ (ii) Mg in ether (iii) aqueous alcohol

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NSEC 2020 - Question 20

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The Galvanic cell can be represented as Zn / $$\text{Zn}^{2+}$$ (0.1 M) // $$\text{Cu}^{2+}$$ (0.1 M) / Cu.Among the following,  the cell among the following that can produce an EMF more than that of this Galvanic cell is
($$E^\circ$$ of $$\text{Zn}^{2+}/\text{Zn}$$ and $$\text{Cu}^{2+}/\text{Cu}$$ are $$-0.763$$ V and 0.337 V respectively)

A

Zn / $$\text{Zn}^{2+}$$ (0.1 M) // $$\text{Cu}^{2+}$$ (0.01 M) / Cu

B

Zn / $$\text{Zn}^{2+}$$ (1 M) // $$\text{Cu}^{2+}$$ (0.01 M) / Cu

C

Zn / $$\text{Zn}^{2+}$$ (0.01 M) // $$\text{Cu}^{2+}$$ (1 M) / Cu

D

Zn / $$\text{Zn}^{2+}$$ (0.01 M) // $$\text{Cu}^{2+}$$ (0.01 M) / Cu

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NSEC 2020 - Question 21

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The correct match of the molecules in column I and reactions in column II

A

i)-N ii)-L iii)-O iv)-M

B

i)-O ii)-N iii)-L iv)-P

C

i)-P ii)-O iii)-L iv)-M

D

i)-P ii)-N iii)-O iv)-L

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NSEC 2020 - Question 22

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While doing a titration, a student recorded a burette reading of 10.0 mL for the neutralization of 10.0 mL $$\text{NaHC}_2\text{O}_4$$ (aq) with 0.1 M NaOH (aq). In a separate experiment, 10.0 mL of this $$\text{NaHC}_2\text{O}_4$$ (aq) solution could be completely oxidized by 10.0 mL of $$\text{KMnO}_4$$ in an acidic medium. What would be the molarity of $$\text{KMnO}_4$$ used by this student?

A

0.02 M

B

0.04 M

C

0.1 M

D

0.2 M

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NSEC 2020 - Question 23

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Pheromones are chemicals that animals produce for social response. The structure of brevicomin, a pheromone, is shown below. The open chain ketodiol that would form brevicomin is

A

7,8-dihydroxynonan-3-one

B

6,7-dihydroxynonan-3-one

C

7,8-dihydroxynonan-2-one

D

6,7-dihydroxynonan-2-one

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NSEC 2020 - Question 24

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The best reagents and conditions to accomplish the following conversion is

A

(i) $$\text{LiAlH}_4$$ in ether, (ii) 3 moles of $$\text{CH}_3\text{I}$$ followed by heating with AgOH

B

(i) $$\text{LiAlH}_4$$ in ether, (ii) $$\text{P}_2\text{O}_5$$ and heat

C

(i) 20% $$\text{H}_2\text{SO}_4$$ and heat, (ii) $$\text{P}_2\text{O}_5$$ and heat

D

$$\text{H}_2$$ and Lindlar catalyst

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NSEC 2020 - Question 25

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The correct statements among the following are

A

Intermolecular forces in n-heptane are stronger than those in 2-methylheptane

B

Boiling point of 2,2-dimethylpentane is higher than that of 2,2-dimethylbutane

C

Both hydrogen bonding and van der Waals forces exist between molecules of 2-methylbutan-2-ol

D

In 2,2-dimethylbutane, primary, secondary and tertiary types of carbon atoms are present

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NSEC 2020 - Question 26

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Which of the following aqueous solutions will have a pH value between 4.0 and 5.0 at $$25^\circ\text{C}$$?

A

0.01 M solution of benzoic acid with $$K_a = 6.6 \times 10^{-5}$$ at $$25^\circ\text{C}$$

B

0.02 mol benzoic acid and 0.05 mol sodium benzoate dissolved in appropriate amount of water to make a solution of 1 L

C

A mixture of 999 mL water and 1 mL of 0.2 M HCl

D

499 mL of 0.01 M NaOH and 501 mL of 0.01 M HCl mixed together

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NSEC 2020 - Question 27

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The energy required to remove an electron from a gaseous species X to form $$\text{X}^+$$ is known as the first ionization energy (IE) of X, the energy required to remove an electron from $$\text{X}^+$$ to form $$\text{X}^{++}$$ is the second IE of X, and similarly the energy required to remove an electron from $$\text{X}^-$$ to form X is called the IE of $$\text{X}^-$$. Identify the correct statements from the following

A

The second IE of the He atom is four times that of the first IE of the H atom

B

The first IEs of F, Ne and Na atoms follow the order IE(Na) < IE(Ne) < IE(F)

C

The second IE of the $$\text{H}^-$$ ion is much less than the first IE of the H atom

D

The IEs of Li, Na and K atoms follow the order IE(K) < IE(Na) < IE(Li)

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NSEC 2020 - Question 28

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The products formed in the following reaction are

A

A

B

B

C

C

D

D

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NSEC 2020 - Question 29

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Which of the following options are correct?

A

$$\text{C}_2$$ is paramagnetic

B

$$\text{He}_2^+$$ has the same energy as that of two isolated He atoms

C

$$\text{S}_2$$ is paramagnetic and $$\text{S}_2^{2-}$$ is diamagnetic

D

$$\text{N}_2^+$$ and $$\text{N}_2$$ have the same bond order

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NSEC 2020 - Question 30

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Nitromethane undergoes an aldol type reaction with a racemic mixture of 2-methylcyclohexanone in presence of aqueous NaOH in two steps I and II to give the product P. The statements NOT correct among the following are

A

The equilibrium in step I will be more towards the right as water is a stronger acid than nitromethane

B

The carbanion formed in reaction I can be stabilized due to resonance

C

The product formed will be a mixture of four stereoisomers in the form of two pairs of enantiomers

D

The mixture of products formed can be readily dehydrated to give a single product

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NSEC 2020 - Question 31

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The structures of hydrogen peroxide $$\text{H}_2\text{O}_2$$ in the solid and gaseous states are given below. Liquid $$\text{H}_2\text{O}_2$$ is slightly more viscous than liquid $$\text{H}_2\text{O}$$. The correct options among the following are

A

Both O atoms are near enough to cause repulsion between the electron lone pairs thus making the O-O bond susceptible for cleavage

B

The strong intermolecular H-bonding along with restricted rotation present in the liquid state of $$\text{H}_2\text{O}_2$$ make it more viscous than liquid $$\text{H}_2\text{O}$$

C

The molecule gets twisted to minimize the repulsion between the lone pair and bond pair of electrons

D

The difference in the dihedral angles in the solid and gaseous states is a consequence of hydrogen bonding between the molecules

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NSEC 2020 - Question 32

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Viruses are nonliving complex chemical entities. They undergo inactivation and hence lose the ability to infect a host, with time. Concentration, (expressed as median tissue culture infectious dose TCID/ml, a unit used in expressing virus concentrations) vs. time plots of a corona virus on the surfaces of a paper currency note and a plastic currency note are shown below. Both these plots have two separate regions, shown by vertical lines in the plots, indicating two time zones.

The correct options among the following are

A

Inactivation of the virus follows zero order kinetics in the first zone and first order kinetics in the second zone

B

The rate of inactivation is independent of the surface material

C

The virus reacts with different chemical entities or substances in the first zone and second zone

D

On both the surfaces, at least 95 percent of the virus is inactivated within 10 h

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