datavorous/entrance-exam-dataset huggingface dataset:
Which of the following sequence correctly represents the decreasing acid nature of oxides

Options:
A $\mathrm{Li}_2 \mathrm{O}\gt\mathrm{BeO}\gt\mathrm{B}_2 \mathrm{O}_3\gt\mathrm{CO}_2\gt\mathrm{N}_2 \mathrm{O}_3$
B $\mathrm{N}_2 \mathrm{O}_3\gt\mathrm{CO}_2\gt\mathrm{B}_2 \mathrm{O}_3\gt\mathrm{BeO}\gt\mathrm{Li}_2 \mathrm{O}$
C $\mathrm{CO}_2\gt\mathrm{N}_2 \mathrm{O}_3\gt\mathrm{B}_2 \mathrm{O}_3\gt\mathrm{BeO}\gt\mathrm{Li}_2 \mathrm{O}$
D $\mathrm{B}_2 \mathrm{O}_3\gt\mathrm{CO}_2\gt\mathrm{N}_2 \mathrm{O}_3\gt\mathrm{Li}_2 \mathrm{O}\gt\mathrm{BeO}$

The correct answer is:
$\mathrm{N}_2 \mathrm{O}_3\gt\mathrm{CO}_2\gt\mathrm{B}_2 \mathrm{O}_3\gt\mathrm{BeO}\gt\mathrm{Li}_2 \mathrm{O}$

Solution:
On passing from left to right in a period acidic character of the normal oxides of the element goes on increasing with increase in electronegativity.

Topic: Chemistry, Classification of Elements and Periodicity in Properties, JEE Main
Which of the following series correctly represents relations between the elements from $\mathrm{X}$ to $\mathrm{Y}$ ? $\mathrm{X} \rightarrow \mathrm{Y}$

Options:
A
${ }_3 \mathrm{Li} \rightarrow{ }_{19} \mathrm{~K}$ Ionization enthalpy increases

B
${ }_9 \mathrm{~F} \rightarrow{ }_{35} \mathrm{Br}$ Electron gain enthalpy (negative sign) increases

C
${ }_6 \mathrm{C} \rightarrow{ }_{32} \mathrm{Ge}$ Atomic radii increases

D
${ }_{18} \mathrm{Ar} \rightarrow{ }_{54} \mathrm{Xe}$ Noble character increases

The correct answer is:
${ }_6 \mathrm{C} \rightarrow{ }_{32} \mathrm{Ge}$ Atomic radii increases

Solution:
On moving down a group atomic radii increases.

Topic: Chemistry, Classification of Elements and Periodicity in Properties, JEE Main, JEE Main 2014 (11 Apr Online)
Which of the following series, lie in visible spectrum?

Options:
A Lyman
B Balmer
C Paschen
D found

The correct answer is:
Balmer

Solution:
The correct option is $2$ Balmer series lies in the visible region.

Topic: Physics, Atomic Physics, JEE Main
Which of the following set contains pair of elements that do not belong to same group but show chemical resemblance?

Options:
A \( \mathrm{Hf}, \mathrm{Zr} \)
B \( \mathrm{K}, \mathrm{Rb} \)
C \( \mathrm{Be}, \mathrm{Al} \)
D \( \mathrm{B}, \mathrm{Al} \)

The correct answer is:
\( \mathrm{Be}, \mathrm{Al} \)

Solution:
1.

Hf and Zr both are d block elements, both belonging to the group 4 of the periodic table.

2.

K and Rb both are S block elements, both belonging to the group 1 of the periodic table.

3.

Be belongs to the group 2 and Al belongs to the group 13 of the periodic table.

But they show resemblance in properties due to:

a) similar charge/ size ratio

b) similar electronegativity.

This is due to the diagonal relationship between

Be and Al.

4) B and Al both are p block elements, both belonging to group 13 of the periodic table.

Topic: Chemistry, s Block Elements, JEE Main
Which of the following set is having correct statements?
1. H2O2 is a weak base
2.  H 2 O 2 oxidizes Fe (II) to Fe (III)
3. H2O2 can be obtained by the electrolysis of conc. H2SO4
4.  H 2 O 2 reduces Mn (VII) to Mn (II)

Options:
A 2, 3
B 3, 4
C 2, 3, 4
D 1, 2, 3, 4

The correct answer is:
2, 3, 4

Solution:
Here statements 2, 3 and 4 are correct as follows
H2O2 is weakly acidic, but more acidic than water.
H2O2+H2O→H3O++HO2-
2Fe2++H2O2+2H+→2Fe3++2H2O
H2SO4⇌H++HSO4-
The peroxy disulphuric acid is hydrolysed separately to get H2O2 .
H2S2O8+H2O→H2SO5+H2SO4
H2SO5+H2O→H2SO4+H2O2
2MnO4-+5H2O2+6H+→2Mn2++8H2O+5O2

Topic: Chemistry, s Block Elements, JEE Main
Which of the following set is having correct statements for enzyme catalysis?
1. Each enzyme is specific for a given reaction
2. The enzyme activity is maximum at optimum pH
3. The enzymatic activity is increased in presence of certain substances called co-enzymes
4. The favourable temperature range of enzyme activity is between 50-60 Â°C

Options:
A 1, 3
B 2, 3
C 1, 2, 3
D 1, 2, 3, 4

The correct answer is:
1, 2, 3

Solution:
Here statement 1, 2 and 3 are correct and 4 one is incorrect as the favourable temperature range for enzymatic activity is 25-37°C . enzymatic activity is destroyed at about 70°C .

Topic: Chemistry, Surface Chemistry, JEE Main
Which of the following set is having correct statements here regarding both B and Al?
1. They combine with nitrogen to form nitrides
2. They react with HCl to form chlorides
3. They burn in oxygen to give oxides at high temperature
4. Their halides are Lewis acids

Options:
A 1, 4
B 3, 4
C 1, 3, 4
D 1, 2, 3, 4

The correct answer is:
1, 3, 4

Solution:
Both B and Al can react with nitrogen to form nitride as follows
2B+N2→2BN
2Al+N2→2AlN
Boron is not attacked by HCl; while Al reacts with HCl to from AlCl3 and H2(g) .
Both B and Al can react with oxygen to form their oxides.
4B+3O2→2B2O3
4Al+3O2→2Al2O3
Halides of both (BX3,AlX3) are electron deficient molecule, so they act as Lewis acids.

Topic: Chemistry, p Block Elements (Group 13 & 14), JEE Main
Which of the following set of characteristics of a material is suitable for using it as a dielectric in a capacitor?

Options:
A large dielectric constant and high dielectric strength
B large dielectric constant and low dielectric strength
C small dielectric constant and high dielectric strength
D small dielectric constant and low dielectric strength

The correct answer is:
large dielectric constant and high dielectric strength

Solution:
The material suitable for use as a dielectric in a capacitor must have high dielectric strength and large dielectric constant

Topic: Physics, Electrostatics, JEE Main
Which of the following set of elements do not possess $f$-electrons?

Options:
A La, U, Lr
B La, Th, Lr
C La, Ac, Th
D Ce, Ac, Th

The correct answer is:
La, Ac, Th

Solution:
Electronic configurations of
(i) Lanthanum (La) with $(Z=57)$ is
$$
[\mathrm{Xe}]_{54} \cdot 5 d^1 \cdot 6 s^2
$$
(ii) Uranium (U) with $(Z=92)$ is
$$
[\mathrm{Rn}]_{86} \cdot 5 f^3 \cdot 6 d^1 \cdot 7 s^2
$$
(iii) Lawrencium ( $\operatorname{Lr})$ with $(Z=103)$ is
$$
[\mathrm{Rn}]_{86} \cdot 5 f^{14} \cdot 6 d^1 \cdot 7 s^2
$$
(iv)Thorium (Th) with $(Z=90)$ is
$$
[\mathrm{Rn}]_{86} \cdot 5 f^1 \cdot 6 d^1 \cdot 7 s^2 \equiv[\mathrm{Rn}]_{86} 6 d^2 \cdot 7 s^2
$$
(due to nearly same energy of $5 f$ and $6 d$-orbitals).
(v) Actinium (Ac) with $(Z=89)$ is
$$
[\mathrm{Rn}]_{86} \cdot 6 d^1 \cdot 7 s^2
$$
(VI) Cerium (Ce) with $(Z=58)$ is
$$
[\mathrm{Xe}]_{54} \cdot 4 f^1 \cdot 5 d^1 \cdot 6 s^2
$$
On the basis of above given electronic configuration, elements La, Ac, and Th do not possess $f$-electrons.
Hence, option (c) is the correct answer.

Topic: Chemistry, d and f Block Elements, JEE Main
Which of the following set of hormones are supposed to have intracellular receptors?

Options:
A Estrogen, testosterone, aldosterone
B Thyroxine, insulin, glucagon
C Epinephrine, cortisol, ADH
D Oxytocin, glucagon, insulin

The correct answer is:
Estrogen, testosterone, aldosterone

Solution:
Hormones bind to specific hormone receptors (proteins) which are of two types mainly:
A. Membrane-bound receptors (present on the cell membrane of the target cells) - Those hormones (protein or peptide) which bound to the membrane-bound receptors usually do not enter the target cell but generate second messengers like cyclic AMP, IP3, Ca++, etc. which in turn regulate cellular metabolism.
B. Intracellular receptors (receptors present inside the target cells - mostly nuclear receptors) - Hormones (e.g. steroid hormones, iodothyronines, etc.) which bound to intracellular receptors, usually regulate gene expression or chromosome function by the interaction of the hormone-receptor complex with the genome. Various biochemical actions occur resulting in physiological and developmental effects.

Topic: Biology, Chemical Coordination and Integration, NEET
Which of the following sets are correct regarding polymer:

(A) Copolymer : Buna-S

(B) Condensation polymer : Nylon-6,6

(C) Fibres : Nylon-6,6

(D) Thermosetting polymer : Terylene

(E) Homopolymers : Buna-N

Choose the correct answer from given options below

Options:
A A,B and C are correct
B B,C and D are correct
C A,C and E are correct
D A,B and D are correct

The correct answer is:
A,B and C are correct

Solution:
Which of the following set are correct regarding polymer.

Buna -S is copolymer of butadiene + styrene

Nylon -6,6 is condensation polymer of adipic Acid and hexanediamine.

Nylon -6,6 is fibre.

Terylene is fibre not thermosetting polymer

Buna-N is copolymer not Homopolymer

Topic: Chemistry, Polymers, JEE Main, JEE Main 2022 (26 Jun Shift 1)
Which of the following sets of components form homogeneous mixture?

Options:
A Phenol + Water
B Sugar + Benzene
C Silver chloride + Water
D Ethyl alcohol + Water

The correct answer is:
Phenol + Water

Solution:
(Ethyl alcohol + water) system is homogeneous in nature as ethyl alcohol & water are miscible in all the proportion.

Topic: Chemistry, Solutions, JEE Main
Which of the following sets of concurrent forces may be in equilibrium

Options:
A $F_1=3 \mathrm{~N}, F_2=5 \mathrm{~N}, F_3=9 \mathrm{~N}$
B $F_1=3 \mathrm{~N}, F_2=5 \mathrm{~N}, F_3=1 \mathrm{~N}$
C $F_1=3 N, F_2=5 N, F_3=15 \mathrm{~N}$
D $F_1=3 \mathrm{~N}, F_2=5 \mathrm{~N}, F_3=6 \mathrm{~N}$

The correct answer is:
$F_1=3 \mathrm{~N}, F_2=5 \mathrm{~N}, F_3=6 \mathrm{~N}$

Solution:
Range of resultant of $F_1$ and $F_2$ varies between $(3+5)=8 \mathrm{~N}$ and $(5-3)=2 \mathrm{~N}$. It means for some value of angle ( $\theta$ ), resultant 6 can be obtained. So, the resultant of $3 \mathrm{~N}, 5 \mathrm{~N}$ and $6 \mathrm{~N}$ may be zero and the forces may be in equilibrium.

Topic: Physics, Laws of Motion, JEE Main
Which of the following sets of phenomena leads to variation in DNA?

Options:
A Linkage, mutation
B Recombination, linkage
C Mutation, recombination
D Aneuploidy, linkage

The correct answer is:
Mutation, recombination

Solution:
A mutation refers to a change in the nucleotide sequence of a short region of DNA. On the other hand, recombination reconstructs a part of the genome. The main difference between mutation and recombination is that mutation brings a small-scale rearrangement in the genome whereas recombination brings a large-scale rearrangement in the genome. Both are responsible for evolution.

Topic: Biology, Principles of Inheritance and Variation, NEET
Which of the following sets of quantum numbers is correct for an electron in $4 \mathrm{f}$ orbital?

Options:
A
$n=4, \mathrm{l}=3, \mathrm{~m}=+4, \mathrm{~s}=+\frac{1}{2}$

B
$n=3, I=2, m=-2, S=+\frac{1}{2}$

C
$n=4, I=3, m=+1, s=+\frac{1}{2}$

D
$n=4, I=4, m-4, s=-\frac{1}{2}$

The correct answer is:
$n=4, I=3, m=+1, s=+\frac{1}{2}$

Solution:
$4 \mathrm{f} \longrightarrow \mathrm{n}=4$
$\mathrm{l}=3$
$m=-\mathrm{l}$ to $+1$
$-3$ to $+3$

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2004
Which of the following sets of quantum numbers is not allowed?

Options:
A n=3, l=2, ml=0, s=+12
B n=3, l=2, ml=-2, s=+12
C n=3, l=3, ml=-3, s=-12
D n=3, l=0, ml=0, s=-12

The correct answer is:
n=3, l=3, ml=-3, s=-12

Solution:
The possible values of principal quantum number 'n' can be any positive integer.

For a particular value of 'n', the possible values of azimuthal quantum number is from 0 to n-1.

Thus, for n=3, the possible 'l' values are 0, 1, 2.

The possible values of magnetic quantum number 'm' is from '-l' to '+l'.

Thus, for l=2, the possible values of 'm' are -2, -1, 0, +1, +2.

The possible values of spin quantum number 's' is -12 and +12.

In option C.

⇒ l=3, not possible for n=3

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2022 (25 Jul Shift 1)
Which of the following sets of quantum numbers represent an impossible arrangement?

Options:
A $\begin{array}{ll} n & l & m & m_s \\ 3 & 2 & -2 & (+) \frac{1}{2} \end{array}$
B $\begin{array}{ll} n & l & m & m_s \\ 4 & 0 & 0 & (-) \frac{1}{2} \end{array}$
C $\begin{array}{ll} n & l & m & m_s \\ 3 & 2 & 0 & (+) \frac{1}{2} \end{array}$
D $\begin{array}{ll} n & l & m & m_s \\ 5 & 3 & 0 & (-) \frac{1}{2} \end{array}$

The correct answer is:
$\begin{array}{ll} n & l & m & m_s \\ 3 & 2 & 0 & (+) \frac{1}{2} \end{array}$

Solution:
If $I=2 m \neq-3 .=(-e$ to $+e)$.

Topic: Chemistry, Structure of Atom, JEE Main
Which of the following sets of quantum numbers represents the highest energy of an atom?

Options:
A
$\mathrm{n}=3, \mathrm{~l}=2, \mathrm{~m}=1, \mathrm{~s}=+1 / 2$

B
$\mathrm{n}=3, \mathrm{~l}=2, \mathrm{~m}=1, \mathrm{~s}=+1 / 2$

C
$\mathrm{n}=4, \mathrm{~l}=0, \mathrm{~m}=0, \mathrm{~s}=+1 / 2$

D
$\mathrm{n}=3, \mathrm{~l}=0, \mathrm{~m}=0, \mathrm{~s}=+1 / 2$

The correct answer is:
$\mathrm{n}=3, \mathrm{~l}=2, \mathrm{~m}=1, \mathrm{~s}=+1 / 2$

Solution:
(B) is the correct option because it has the maximum value of $n+\ell$
Hence, (B) is correct.

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2007
Which of the following sets of reactants is used for preparation of paracetamol from phenol?

Options:
A HNO3, H2/Pd, CH3 CO2O
B H2SO4,Â H2/Pd,Â CH3Â CO2O
C C6H5N2Cl,Â SnCl2/HCl,Â Â CH3CO2O
D Br2/H2O,Â Â Zn/HCl,Â CH3CO2O

The correct answer is:
HNO3, H2/Pd, CH3 CO2O

Solution:

Topic: Chemistry, Chemistry in Everyday Life, JEE Main
Which of the following shall form an octahedral complex

Options:
A $d^4$ (low spin)
B $d^8$ (high spin)
C $d^6$ (low spin)
D None of these

The correct answer is:
$d^6$ (low spin)

Solution:
The compounds which show configuration are octahedral complexes.

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the following show an increase in entropy?

I. Boiling of water

II. Melting of ice

III. Freezing of water

IV. Formation of hydrogen gas from water

Options:
A (I) and (II)
B Only (III)
C (I), (II) and (IV)
D (III) and (IV)

The correct answer is:
(I), (II) and (IV)

Solution:
Entropy is the measure of disorderliness. It means as disorderliness increases entropy increases.

Melting of ice leads to the formation of liquid water where the particles are in random motion which leads to an increase in entropy.

Option (c) is the correct option as in (i),(ii) and (iv) the state changes towards more random state, thus entropy increases.

Topic: Chemistry, Thermodynamics (C), JEE Main
Which of the following shows maximum magnetic moment?

Options:
A Mg2+
B Ti3+
C V3+
D Fe2+

The correct answer is:
Fe2+

Solution:
More be the number of unpaired electrons → more be the magnetic moment.

and

Number of unpaired electrons in Mg2+=0

Number of unpaired electrons in Ti3+=1

Number of unpaired electrons in V3+=2

Fe2+=4

Number of unpaired electrons in

Thus, Fe2+ show maximum value of magnetic moment (μ).

also, μ=n(n+2). BM (n= Number of unpaired electrons).

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the following shows the correct relationship between the pressure 'P' and density ρ of an ideal gas at constant temperature ?

Options:
A

B

C

D

The correct answer is:

Solution:
ρ = PM RT
P = ρ RT M
P ∝ ρ

Topic: Physics, Kinetic Theory of Gases, JEE Main
Which of the following shows the correct relationship between the pressure 'P' and density ρ of an ideal gas at constant temperature ?

Options:
A

B

C

D

The correct answer is:

Solution:
ρ = PM RT
P = ρ RT M
P ∝ ρ

Topic: Physics, Kinetic Theory of Gases, JEE Main, JEE Main 2016 (10 Apr Online)
Which of the following sign indicate that the sugar is actually 'dextrorotatory'

Options:
A $-$
B $+$
C $R-$
D All of these

The correct answer is:
$+$

Solution:
A dextrorotatory compound is often prefixed with "(+)-"

Topic: Chemistry, Biomolecules, JEE Main
Which of the following situations correctly describe the similarity between an angiospermic egg and a human egg?
I. Eggs of both are formed only once in a lifetime.
II. Both the angiosperm egg and human egg are stationary.
III. Both the angiosperm egg and human egg are motile transported.
IV. Syngamy in both results in the formation of zygote. Choose the correct answer from the options below.

Options:
A
nodes are shorter than internodes

B
nodes have meristamatic cells

C
nodes are located near the soil

D
nodes have non-photosynthetic cells

The correct answer is:
nodes have meristamatic cells

Solution:
In case of many terrestrial organisms (including both angiosperms and humans) that exhibit internal fertilisation, syngamy occurs inside the body of the organism to form zygote.
Throughout the reproductive phase both the angiosperm and human remains reproductively active. It means the formation of egg takes place not only once but many times in a lifetime.
In humans, once an egg has been released from ovary, the beating of cillia in the fallopian tube moves the egg from the ovary to the uterus. So, the egg is considered as motile not stationary.
In flowering plants (angiosperms), the gametes are nonmotile cells within gametophytes, but for the fusion to take place the non-motile male gametes are carried to female gamete by pollen-tubes.

Topic: Biology, Reproduction in Organisms
Which of the following sketches is an isobars (Given: nR P >1 )

Options:
A
B
C
D

The correct answer is:

Solution:
At constant pressure
PV = nRT
V=nRPT
so, log⁡V=log⁡nRP+log⁡T
compare this with y=mx+c

Topic: Chemistry, States of Matter, JEE Main
Which of the following solid salt on heating with solid K2Cr2O7 and concentration H2SO4 orange red vapours are evolved which turn aqueous NaOH solution yellow?

Options:
A NaBr
B NaCl
C NaNO3
D NaI

The correct answer is:
NaCl

Solution:
NaCl gives following reactions as follows

Topic: Chemistry, d and f Block Elements, JEE Main
Which of the following sols is negatively charged?

Options:
A Ferric hydroxide
B Aluminium hydroxide
C Arsenious sulphide
D Silver iodide in silver nitrate solution

The correct answer is:
Arsenious sulphide

Solution:
Ferric hydroxide = Positive sol
Aluminium hydroxide = Positive sol
Arsenious sulphide = Negative sol

Topic: Chemistry, Surface Chemistry, JEE Main
Which of the following solutions contains the maximum freezing point?

Options:
A \( 0.01 \mathrm{M} \mathrm{NaCl} \)
B \( 0.01 \mathrm{M} \mathrm{BaCl}_{2} \)
C \( 0.01 \mathrm{M} \) Glucose
D \( 0.001 \mathrm{M} \) Urea

The correct answer is:
\( 0.001 \mathrm{M} \) Urea

Solution:
Freezing point α=1 particle concentration

Topic: Chemistry, Solutions, JEE Main
Which of the following solutions will exactly oxidize $25 \mathrm{~mL}$ of an acid solution of $0.1 \mathrm{M}$ iron () oxalate:

Options:
A $25 \mathrm{~mL}$ of $0.1 \mathrm{M} \mathrm{KMnO} 4$
B $25 \mathrm{~mL}$ of $0.2 \mathrm{M} \mathrm{KMnO} 4$
C $25 \mathrm{~mL}$ of $0.6 \mathrm{M} \mathrm{KMnO} 4$
D $15 \mathrm{~mL}$ of $0.1 \mathrm{M} \mathrm{KMnO} 4$

The correct answer is:
$15 \mathrm{~mL}$ of $0.1 \mathrm{M} \mathrm{KMnO} 4$

Solution:
Milli equivalents of $\mathrm{FeC} 2 \mathrm{O} 4=0.1 \times 3 \times 25=7.5$ From choice (4), milli equivalents of $\mathrm{KMnO} 4=0.1 \times 5 \times 15=7.5$ $\mathrm{m}$. eq. of $\mathrm{FeC} 2 \mathrm{O} 4=\mathrm{m}$. eq. of $\mathrm{KMnO} 4$

Topic: Chemistry, Redox Reactions, JEE Main
Which of the following solutions will have highest boiling point?

Options:
A $0.1 \mathrm{M} \mathrm{FeCl}_{3}$
B $0.1 \mathrm{M} \mathrm{BaCl}_{2}$
C $0.1 \mathrm{M} \mathrm{NaCl}$
D $0.1 \mathrm{M}$ urea $\left(\mathrm{NH}_{2} \mathrm{CONH}_{2}\right)$

The correct answer is:
$0.1 \mathrm{M} \mathrm{FeCl}_{3}$

Solution:
Elevation in boiling point is a colligative property, ie, depends only on number of particles or ions. $0.1 \mathrm{M} \mathrm{FeCl}_{3}$ gives maximum number of ions, thus has highest boiling point.

Topic: Chemistry, Solutions, JEE Main
Which of the following species exhibits the diamagnetic behaviour?

Options:
A
$\mathrm{O}_2^{2-}$

B
$\mathrm{O}_2^{+}$

C
$\mathrm{O}_2$

D
$\mathrm{NO}$

The correct answer is:
$\mathrm{O}_2^{2-}$

Solution:
The correct option is $\mathrm{O}_2^{2-}$
This species has $18 \mathrm{~e}^{-}$, which are filled in such a way that all molecular orbitals are fully filled, so diamagnetic.
$\mathrm{\sigma 1 s^2 \sigma^* 1 s^2, \sigma 2 s^2 \sigma^* 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2=\pi 2 p_y^2, \pi^* 2 p_x^2=\pi^* 2 p_y^2}$
Hence, (A) is correct.

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2007
Which of the following species has the highest electron affinity

Options:
A $F$
B $0$
C $0^{-}$
D $\mathrm{Na}^{+}$

The correct answer is:
$F$

Solution:
Halogens have the highest $e^{-}$affinity.

Topic: Chemistry, Classification of Elements and Periodicity in Properties, JEE Main
Which of the following species is not electrophilic in nature?

Options:
A $\stackrel{\oplus}{\mathrm{Cl}}$
B $\mathrm{BH}_3$
C $\mathrm{H}_3 \stackrel{\oplus}{\mathrm{O}}$
D $\stackrel{\oplus}{\mathrm{N}} \mathrm{O}_2$

The correct answer is:
$\mathrm{H}_3 \stackrel{\oplus}{\mathrm{O}}$

Solution:
Electrophiles are electron deficient species. Among the given, $\mathrm{H}_3 \mathrm{O}^{\oplus}$ has lone pair of electrons for donation, thus it is not electron deficient and hence, does not behave like an electrophile.

Topic: Chemistry, Ionic Equilibrium, NEET, NEET 2010 (Mains)
Which of the following species is not paramagnetic?

Options:
A CO
B O2
C B2
D NO

The correct answer is:
CO

Solution:
CO has no unpaired electron while other have unpaired electrons so, paramagnetic in nature.(Apply M.O.T)
Molecular orbital configuration⇒
CO :like N2 ; σ1s2<σ*1S2<σ2S2<σ*2S2<π2Px2= π2Py2<σ2Pz2  (No unpaired electrons)
O2 :σ1S2<σ*1S2<σ2S2<σ*2S2<σ2Pz2<π2Px2=π2Py2<π*2Px1= π*2Py1  (2unpaired electrons)
B2:σ1S2<σ*1S2<σ2S2<σ*2S2<π2Px1=π2Py1 (2unpaired electrons)
NO : σ1S2<σ*1S2<σ2S2<σ*2S2<σ2Pz2<π2Px2=π2Py2<π*2Py1= π*2Px0(1unpaired electrons)

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2017 (02 Apr)
Which of the following species is paramagnetic in nature

Options:
A Free radical
B Carbonium ion
C Carbanion
D All the above

The correct answer is:
Carbanion

Solution:
Without intermediate reaction take place as under
(According to markownikoff rule)
But the halogen bonded with terminal carbon so it take place in presence of peroxide by free radical mechanism.
$\underset{\text { peroxide }}{-O-O R} \rightarrow 2 R \dot{O} ; \mathrm{HBr}+\dot{\mathrm{RO}} \rightarrow \mathrm{ROH}+\mathrm{Br}$.
$\mathrm{CH}_3-\mathrm{CH}=\mathrm{CH}_2+\mathrm{Br} \rightarrow \mathrm{CH}_3-\mathrm{C} \dot{\mathrm{H}}-\mathrm{CH}_2-\mathrm{Br}$
$\mathrm{CH}_3-\mathrm{C} \mathrm{H}-\mathrm{CH}_2 \mathrm{Br}+\mathrm{HBr} \rightarrow$ $\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2 \mathrm{Br}+\mathrm{Br}$.

Topic: Chemistry, General Organic Chemistry, JEE Main
Which of the following species is paramagnetic in nature?

Options:
A Carbonium ion
B Free radical
C Singlet Carbene
D Nitrene

The correct answer is:
Free radical

Solution:
Species	Valence electrons	Magnetic behavior

Carbonium ion	6	Diamagnetic

Free radical	7	Paramagnetic

Carbene	6	Diamagnetic

Nitrene	6	Diamagnetic

Topic: Chemistry, General Organic Chemistry, JEE Main
Which of the following spectrochemical series is TRUE?

Options:
A \( \mathrm{SCN}^{-} < \mathrm{NH}_{3} < \mathrm{F}^{-} < \)en \( < \mathrm{CO} \)
B \( \mathrm{SCN}^{-} < \mathrm{F}^{-} < \mathrm{NH}_{3} < \) en \( < \mathrm{CO} \)
C \( \mathrm{SCN}^{-} < \mathrm{F}^{-} < \mathrm{en} < \mathrm{NH}_{3} < \mathrm{CO} \)
D \( \mathrm{SCN}^{-} < \mathrm{F}^{-} < \)en \( < \mathrm{CO} < \mathrm{NH}_{3} \)

The correct answer is:
\( \mathrm{SCN}^{-} < \mathrm{F}^{-} < \mathrm{NH}_{3} < \) en \( < \mathrm{CO} \)

Solution:
As the electronegativity of electron donating atom increases, its electron donating tendency decreases. Hence, the correct order of spectrochemical series:

SCN-<F-<NH3<en<CO

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the following statement about anhydrous aluminum chloride is correct?

Options:
A It fumes in moist air.
B It exists as dimer both in the vapor state below 350oC and in non-polar solvents
C It is prepared by heating Al2O3 in a stream of Sulphur chloride ( S2Cl2 ) vapor and chlorine.
D All of these

The correct answer is:
All of these

Solution:
(i) AlCl3+3H2O→AlOH3+3HCl↑fumes
(ii) It exists as dimer in non-polar solvents like benzene and in vapour state below 350oC .
(iii) 4Al2O3+3S2Cl2+9Cl2→8AlCl3+6SO2↑
A,B,C are correct D

Topic: Chemistry, p Block Elements (Group 13 & 14), JEE Main