NSEC 2021 Question Paper

NSEC 2021 - Question 1

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The correct order of CFSE of the following complex ions is $$[\text{Zn}(\text{NH}_3)_4]^{2+}$$, $$[\text{Co}(\text{NH}_3)_6]^{2+}$$, $$[\text{Co}(\text{NH}_3)_6]^{3+}$$, $$[\text{Ir}(\text{NH}_3)_6]^{3+}$$

A

$$[\text{Ir}(\text{NH}_3)_6]^{3+} > [\text{Co}(\text{NH}_3)_6]^{3+} > [\text{Co}(\text{NH}_3)_6]^{2+} > [\text{Zn}(\text{NH}_3)_4]^{2+}$$

B

$$[\text{Zn}(\text{NH}_3)_4]^{2+} > [\text{Co}(\text{NH}_3)_6]^{2+} > [\text{Co}(\text{NH}_3)_6]^{3+} > [\text{Ir}(\text{NH}_3)_6]^{3+}$$

C

$$[\text{Ir}(\text{NH}_3)_6]^{3+} > [\text{Co}(\text{NH}_3)_6]^{3+} > [\text{Zn}(\text{NH}_3)_4]^{2+} > [\text{Co}(\text{NH}_3)_6]^{2+}$$

D

$$[\text{Co}(\text{NH}_3)_6]^{3+} > [\text{Ir}(\text{NH}_3)_6]^{3+} > [\text{Co}(\text{NH}_3)_6]^{2+} > [\text{Zn}(\text{NH}_3)_4]^{2+}$$

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NSEC 2021 - Question 2

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Solvents are classified as polar and nonpolar based on their dipole moments. Given below are some solvents.
(p) 1,2-dibromobenzene (q) diisopropylether (r) trans-1,2-dichloroethene
(s) 1,2-dichloroethane (t) N-ethyl-N-methylpropan-1-amine
The set in which all solvents are polar is

A

p, s, t

B

p, q, r

C

r, s, t

D

q, r, t

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NSEC 2021 - Question 3

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Which of the following statement/s is/are correct?
I. Half-life is 50 % of the total time taken for the completion of a reaction
II. Collision frequency (Z), which is the number of collisions per second per unit volume, is same as the rate constant of the reaction
III. A change in the activation energy of a reaction at a particular temperature will result in a proportional change in the rate and rate constant of the reaction at the same temperature
IV. All first order reactions are not unimolecular
V. For a zero order reaction, slope of a plot of $$t_{1/2}$$ Vs. initial concentration will be zero

A

I, IV

B

II only

C

IV only

D

II, III, V

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NSEC 2021 - Question 4

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The orange colour of $$\text{K}_2\text{Cr}_2\text{O}_7$$ and yellow colour of $$\text{K}_2\text{CrO}_4$$ are, respectively, due to

A

charge transfer transitions and d-d transitions

B

d-d transitions and charge transfer transitions

C

charge transfer transitions in both

D

d-d transitions in both

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NSEC 2021 - Question 5

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One mole of neon (atomic mass = $$20\ \text{g mol}^{-1}$$) and one mole of argon (atomic mass = $$40\ \text{g mol}^{-1}$$) are stored in two separate containers I and II, at temperature $$T$$ and $$2T$$ respectively. If both the gases are assumed to behave ideally

A

K.E. and average velocity of the gas molecules will be the same in both I and II

B

K.E. and average velocity of the gas molecules in II will be twice that of the gas molecules in I

C

K.E. of the gas molecules in II will be twice that in I and average velocity of the gas molecules in both I and II will be the same

D

Both K.E. and average velocity of the gas molecules in I will be twice that of the gas molecules in II

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NSEC 2021 - Question 6

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An aldehyde/ketone in the presence of a base forms a carbanion at the $$\alpha$$-position which can react with a carbonyl group in an Aldol type of reaction. It can also react with an olefinic double bond which is activated by groups like CO, CN, $$\text{NO}_2$$ attached to the double bond. The latter reaction is an addition reaction across the double bond. Wieland-Miescher ketone is an important synthetic intermediate used to synthesize many compounds

The pair of starting materials suitable for preparation of Wieland-Miescher ketone through a base catalysed reaction is

A

B

C

D

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NSEC 2021 - Question 7

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X in the following reaction is

A

2,2-Dimethyl-1,3-propanediol

B

2-Methylpropan-1-ol

C

iso-butyric acid

D

3-Hydroxy-2,2-dimethylpropanal

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NSEC 2021 - Question 8

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When 0.805 g of the potassium salt $$(\text{CH}_2)_n(\text{COOK})_2$$ of a dibasic organic acid was reduced, 0.323 g of potassium was obtained. Molar mass of the acid is

A

194

B

116

C

118

D

156

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NSEC 2021 - Question 9

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Among (i) HCl, (ii) HOClO, (iii) $$\text{HOClO}_2$$ and (iv) $$\text{HOClO}_3$$, which cannot undergo a disproportionation reaction?

A

Only (i)

B

(ii) and (iii)

C

(i) and (iv)

D

(ii), (iii) and (iv)

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NSEC 2021 - Question 10

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The electronic transition in $$\text{He}^+$$ ion that will occur at the same wavelength as that of the $$n = 2$$ to $$n = 1$$ transition in H atom is

A

$$n = 2$$ to $$n = 1$$

B

$$n = 3$$ to $$n = 1$$

C

$$n = 3$$ to $$n = 2$$

D

$$n = 4$$ to $$n = 2$$

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NSEC 2021 - Question 11

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P in the following reaction is

A

A

B

B

C

C

D

D

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NSEC 2021 - Question 12

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The number of stereoisomers is maximum for (ox = $$\text{C}_2\text{O}_4^{2-}$$)

A

$$[\text{Co}(\text{ox})_3]^{3-}$$

B

$$[\text{Co}(\text{ox})_2\text{ClBr}]^{3-}$$

C

$$[\text{Co}(\text{ox})\text{Cl}_2\text{Br}_2]^{3-}$$

D

$$[\text{CoCl}_3\text{Br}_3]^{3-}$$

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NSEC 2021 - Question 13

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Maximum number of electrons with $$m_s = \frac{1}{2}$$ which can be accommodated in subshells having total three nodes is

A

10

B

16

C

20

D

32

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NSEC 2021 - Question 14

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The Hinsberg test of the compound X produces a solid compound Y that is insoluble in 10 % aq. NaOH. Y dissolves in 10 % aq. sulphuric acid. The compound X is

A

$$\text{NH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{N}(\text{CH}_3)_2$$

B

$$(\text{CH}_3)_2\text{NCH}_2\text{CH}_2\text{NHCH}_3$$

C

$$\text{NH}_2\text{CH}_2\text{C}(\text{CH}_3)_2\text{CH}_2\text{NH}_2$$

D

$$(\text{CH}_3)_2\text{NCH}_2\text{N}(\text{CH}_3)_2$$

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NSEC 2021 - Question 15

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An ionic species, $$\text{M}^{3+}$$, is isoelectronic with $$\text{CuCl}_2$$ and has $$(Z+2)$$ neutrons. The molar mass of $$\text{M}^{3+}$$ is

A

128

B

62

C

68

D

134

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NSEC 2021 - Question 16

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In compound X, the number of chiral centres and the number of peptide linkages are, respectively

A

2,3

B

3,2

C

2,2

D

3,3

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NSEC 2021 - Question 17

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Which of the following reactions is NOT an example of Lewis acid-Lewis base reaction?

A

$$\text{Zn} + \text{I}_3^- \rightarrow \text{Zn}^{2+} + 3\text{I}^-$$

B

$$\text{I}_2 + \text{I}_3^- \rightarrow \text{I}_5^-$$

C

$$\text{CoCl}_3 + \text{Cl}^- \rightarrow \text{CoCl}_4^-$$

D

$$\text{SO}_3 + \text{H}_2\text{O} \rightarrow \text{H}^+ + \text{HSO}_4^-$$

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NSEC 2021 - Question 18

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A student intended to prepare 1000 mL of a 10 ppm solution of $$\text{K}^+$$ from KCl. He made appropriate calculations, weighed the salt accordingly and prepared the solution. However, after making the solution, he realized that the salt he used was $$\text{KNO}_3$$ and not KCl. The concentration of $$\text{K}^+$$ (ppm) in this prepared solution is

A

7.37

B

10.00

C

13.55

D

3.86

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NSEC 2021 - Question 19

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Oxide A is soluble in NaOH, oxide B in HCl and oxide C in both. The correct set of A, B and C is

A

$$\text{A} = \text{CO}_2$$, $$\text{B} = \text{SO}_2$$, $$\text{C} = \text{PbO}_2$$

B

$$\text{A} = \text{CO}_2$$, $$\text{B} = \text{Na}_2\text{O}$$, $$\text{C} = \text{ZnO}$$

C

$$\text{A} = \text{SO}_2$$, $$\text{B} = \text{ZnO}$$, $$\text{C} = \text{SnO}_2$$

D

$$\text{A} = \text{SO}_2$$, $$\text{B} = \text{BaO}$$, $$\text{C} = \text{Na}_2\text{O}$$

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NSEC 2021 - Question 20

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Ascorbic acid (Vitamin C), a naturally occurring water soluble vitamin and abundantly found in lemon, shows antioxidant properties. In ascorbic acid, the OH with the lowest pKa is

A

1

B

2

C

3

D

4

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NSEC 2021 - Question 21

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Compound X $$(\text{C}_7\text{H}_{12}\text{O}_2)$$ gives i) a positive silver mirror test and ii) a yellow precipitate on treatment with $$\text{I}_2/\text{NaOH}$$. The compound X is

A

2-hydroxy-3,3-dimethylcyclopentanone

B

2,5-heptanedione

C

2,2-dimethyl-3-oxopentanal

D

2,2-dimethyl-4-oxopentanal

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NSEC 2021 - Question 22

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If the ratio of the concentrations of the oxidized and reduced forms of a species in an electrochemical reaction can be given as $$\frac{[\text{Ox}]}{[\text{Red}]} = 1.0 \times 10^{-3}$$, the correct expression among the following at $$25^\circ\text{C}$$ is

A

$$E = E^\circ + \frac{1}{3}\left(\frac{0.0592}{n}\right)$$

B

$$E - E^\circ = 3 \times \left(\frac{0.0592}{n}\right)$$

C

$$E = E^\circ - \frac{1}{3}\left(\frac{0.0592}{n}\right)$$

D

$$E - E^\circ = \left(\frac{0.0592}{n}\right)^{1/3}$$

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NSEC 2021 - Question 23

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Among the following numbers, the one in which all the zeros are significant is

A

0.0004

B

0.0400

C

40.000

D

0.0040

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NSEC 2021 - Question 24

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Among the following sets of compounds, the one in which a reaction between them followed by hydrolysis that does not lead to the formation of 1-phenyl-2-butanol is

A

phenylacetaldehyde and ethylmagnesium bromide

B

butanal and phenylmagnesium bromide

C

propanal and benzylmagnesium bromide

D

1-phenyl-2-butanone and $$\text{NaBH}_4$$

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NSEC 2021 - Question 25

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At room temperature, NaCl(s) and KCl(s) were taken in equal masses and dissolved in equal volumes of water in two separate closed containers I and II respectively. Of the following, correct option/s is/are

A

To compare molarities in (I) and (II), masses of both the solutions need to be known

B

Molalities cannot be compared without measuring the mass of water added in each case

C

If (I) and (II) are completely transferred into another container (III), $$[\text{Cl}^-]$$ in (III) will be sum of that in (I) and (II)

D

Information given is sufficient to compare the vapour pressures in (I) and (II)

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NSEC 2021 - Question 26

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In a pair of isomers of molecular formula $$\text{C}_5\text{H}_8$$ both the compounds undergo catalytic hydrogenation to form compounds of molecular formula $$\text{C}_5\text{H}_{10}$$. On ozonolysis followed by oxidative workup $$(\text{H}_2\text{O}_2)$$, one of the isomers gives a diacid $$(\text{C}_5\text{H}_8\text{O}_4)$$ while the other isomer gives a ketoacid $$(\text{C}_5\text{H}_8\text{O}_3)$$. The pair/s which give/s above set of reactions is/are

A

3-ethylcyclopropene and 1-pentyne

B

cyclopentene and 1-methylcyclobutene

C

1-methylcyclobutene and 3-methylcyclobutene

D

1,2-dimethylcyclopropene and 3-methylcyclobutene

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NSEC 2021 - Question 27

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The resonance structures of $$\text{SCN}^-$$ are given below along with the S-C and C-N bond lengths

Among the following, the incorrect statement/s is/ are

A

The contribution from resonance structures (i) and (ii) is more important than that from structure (iii)

B

The formal charge on S in structure (iii) is zero

C

The degree of contribution of these structures is in the order $$\text{i} > \text{ii} > \text{iii}$$

D

The formal charge on N in structure (ii) is zero

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NSEC 2021 - Question 28

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The compound/s which form/s stable hydrate/s is/are

A

a

B

b

C

c

D

d

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NSEC 2021 - Question 29

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The formula/e which also represent/s a compound with formula X is/are

A

a

B

b

C

c

D

d

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NSEC 2021 - Question 30

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Following is the P vs V plot of a cyclic process $$1 \rightarrow 2$$, $$2 \rightarrow 3$$, $$3 \rightarrow 4$$, $$4 \rightarrow 1$$, denoted as I, II, III and IV respectively for a system of one mole of an ideal gas. Assume that there is heat exchange between the system and surroundings only in II and IV. Which of the following is/are correct?

A

In II and IV $$\Delta S$$ is zero

B

In I and III, $$\Delta S$$ is zero

C

I and III are isothermal and reversible

D

In II and IV, change in internal energy of the gas $$(\Delta U)$$ is zero

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NSEC 2021 - Question 31

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For the given compound, % s character of phosphorous hybrid orbitals which contribute to various bonds are given in the table below.

This difference in % s character of various phosphorous bonds could be due to

A

The large size of bromine atom

B

The large electronegativity difference between P and O

C

Increased overlap of $$\sigma$$-orbitals of terminal P-O bond

D

Stronger covalent character of P-O in cyclic oxygen atoms

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NSEC 2021 - Question 32

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$$\beta$$-carotene and related compounds are plant pigments that give red, orange and yellow vegetables their vibrant colour. The structure of $$\beta$$-carotene is given below.

It is approved as a food additive in many countries. The correct statement/s that describe/s $$\beta$$-carotene is/are

A

It is a strong oxidizing agent

B

It reacts with singlet oxygen, an excited form of $$\text{O}_2$$, to produce an epoxide

C

It absorbs red/yellow light of electromagnetic spectrum

D

It comes in the oil phase when carrots are cooked in oil and water in a curry

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