JEE Main 2021 (Online) 24th February Morning Shift
Paper was held on Wed, Feb 24, 2021 3:30 AM
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Chemistry

1
The electrode potential of M2+/M of 3d-series elements shows positive value for :
2
Which of the following reagent is used for the following reaction ?

$$ \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_3 \stackrel{?}{\longrightarrow} \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CHO} $$
3
Which of the following are isostructural pairs ?

A. $$SO_4^{2 - }$$ and $$CrO_4^{2 - }$$

B. SiCl4, and TiCl4

C. NH3 and NO3-

D. BCl3 and BrCl3
4
Consider the elements Mg, Al, S, P and Si, the correct increasing order of their first ionization enthalpy is :
5
Out of the following, which type of interaction is reponsible for the stabilisation of $$\alpha $$-helix structure of proteins ?
6
Which of the following compound gives pink colour on reaction with phthalic anhydride in conc. H2SO4 followed by treatment with NaOH ?
7
Given below are two statements :

Statement I : Colourless cupric metaborate is reduced to cuprous metaborate in a luminous flame.

Statement II : Cuprous metaborate is obtained by heating boric anhydride and copper sulphate in a non-luminous flame.

In the light of the above statements, choose the most appropriate answer from the options given below.
8
In the following reaction the reason why meta-nitro product also formed is :

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Compounds Containing Nitrogen Question 153 English
9
What is the major product formed by HI on reaction with

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Haloalkanes and Haloarenes Question 99 English
10
'A' and 'B' in the following reactions are :

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Compounds Containing Nitrogen Question 152 English
11
Identify products A and B.

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Hydrocarbons Question 89 English
12
What is the final product (major) 'A' in the given reaction ?

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Alcohols, Phenols and Ethers Question 108 English
13
The product formed in the first step of the reaction of

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Haloalkanes and Haloarenes Question 98 English
with excess $$\mathrm{Mg/Et_2O}$$ ($$\mathrm{Et=C_2H_5}$$) is
14
Number of amphoteric compounds among the following is ________.
(A) BeO
(B) BaO
(C) Be(OH)2
(D) Sr(OH)2
15
The stepwise formation of $${\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }}$$ is given below:

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - Chemical Equilibrium Question 59 English
The value of stability constants K1, K2, K3 and K4 are 104, 1.58 x 103, 5 x 102 and 102 respectively.
The overall equilibrium constants for dissociation of $${\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }}$$ is x $$ \times $$ 10-12.
The value of x is ________. (Rounded off to the nearest integer)
16
A proton and a Li3+ nucleus are accelerated by the same potential. If $$\lambda _{Li}$$ and $$\lambda _p$$ denote the de Broglie wavelengths of Li3+ and proton respectively, then the value of $${{{\lambda _{Li}}} \over {{\lambda _p}}}$$ is x $$ \times $$ 10-1.
The value of x is ______. (Rounded off to the nearest integer)
[Mass of Li3+ = 8.3 mass of proton]
17
At 1990 K and 1 atm pressure, there are equal number of Cl2, molecules and Cl atoms in the reaction mixture. The value of Kp for the reaction Cl2 (g) $$ \rightleftharpoons $$ 2Cl(g) under the above conditions is x $$ \times $$ 10-1.
The value of x is _______. (Rounded off to the nearest integer)
18
When 9.45 g of CICH2COOH is added to 500 mL of water, its freezing point drops by 0.5°C. The dissociation constant of CICH2COOH is x $$ \times $$ 10-3.
The value of x is ________. (Rounded off to the nearest integer)
[Kf(H20) = 1.86 K kg mol-1]
19
4.5 g of compound A (MW = 90) was used to make 250 mL of its aqueous solution. The molarity of the solution in M is x $$ \times $$ 10-1.
The value of x is _______. (Rounded off to the nearest integer)
20
The reaction of sulphur in alkaline medium is given below:

JEE Main 2021 (Online) 24th February Morning Shift Chemistry - p-Block Elements Question 153 English
The values of 'a' is _______. (Integer answer)
21
For the reaction A(g) $$ \to $$ B(g) the value of the equilibrium constant at 300 K and 1 atm is equal to 100.0. The value of $$\Delta $$rG for the reaction at 300 K and 1 atm in J mol-1 is – xR, where x is _______. (Rounded off to the nearest integer)
[R = 8.31 J mol–1K-1 and ln 10 = 2.3)
22
Gaseous cyclobutene isomerises to butadiene in a first order process which has a 'k' value of 3.3 $$ \times $$ 10-4 s-1 at 153°C. The time in minutes it takes for the isomerization to proceed 40% to completion at this temperature is ______.
(Rounded off to the nearest integer)

Mathematics

1
If $$\int {{{\cos x - \sin x} \over {\sqrt {8 - \sin 2x} }}} dx = a{\sin ^{ - 1}}\left( {{{\sin x + \cos x} \over b}} \right) + c$$, where c is a constant of integration, then the ordered pair (a, b) is equal to :
2
If f : R $$ \to $$ R is a function defined by f(x)= [x - 1] $$\cos \left( {{{2x - 1} \over 2}} \right)\pi $$, where [.] denotes the greatest integer function, then f is :
3
The population P = P(t) at time 't' of a certain species follows the differential equation

$${{dP} \over {dt}}$$ = 0.5P – 450. If P(0) = 850, then the time at which population becomes zero is :
4
Let f : R → R be defined as f (x) = 2x – 1 and g : R - {1} → R be defined as g(x) = $${{x - {1 \over 2}} \over {x - 1}}$$. Then the composition function f(g(x)) is :
5
The function
f(x) = $${{4{x^3} - 3{x^2}} \over 6} - 2\sin x + \left( {2x - 1} \right)\cos x$$ :
6
$$\mathop {\lim }\limits_{x \to 0} {{\int\limits_0^{{x^2}} {\left( {\sin \sqrt t } \right)dt} } \over {{x^3}}}$$ is equal to :
7
A scientific committee is to be formed from 6 Indians and 8 foreigners, which includes at least 2 Indians and double the number of foreigners as Indians. Then the number of ways, the committee can be formed, is :
8
A man is walking on a straight line. The arithmetic mean of the reciprocals of the intercepts of this line on the coordinate axes is $${1 \over 4}$$. Three stones A, B and C are placed at the points (1, 1), (2, 2) and (4, 4) respectively. Then, which of these stones is / are on the path of the man?
9
Let p and q be two positive numbers such that p + q = 2 and p4+q4 = 272. Then p and q are roots of the equation :
10
The area (in sq. units) of the part of the circle x2 + y2 = 36, which is outside the parabola y2 = 9x, is :
11
If $${e^{\left( {{{\cos }^2}x + {{\cos }^4}x + {{\cos }^6}x + ...\infty } \right){{\log }_e}2}}$$ satisfies the equation t2 - 9t + 8 = 0, then the value of
$${{2\sin x} \over {\sin x + \sqrt 3 \cos x}}\left( {0 < x < {\pi \over 2}} \right)$$ is :
12
The locus of the mid-point of the line segment joining the focus of the parabola y2 = 4ax to a moving point of the parabola, is another parabola whose directrix is :
13
The system of linear equations
3x - 2y - kz = 10
2x - 4y - 2z = 6
x+2y - z = 5m
is inconsistent if :
14
Let P = $$\left[ {\matrix{ 3 & { - 1} & { - 2} \cr 2 & 0 & \alpha \cr 3 & { - 5} & 0 \cr } } \right]$$, where $$\alpha $$ $$ \in $$ R. Suppose Q = [ qij] is a matrix satisfying PQ = kl3 for some non-zero k $$ \in $$ R.
If q23 = $$ - {k \over 8}$$ and |Q| = $${{{k^2}} \over 2}$$, then a2 + k2 is equal to ______.
15
The minimum value of $$\alpha $$ for which the
equation $${4 \over {\sin x}} + {1 \over {1 - \sin x}} = \alpha $$ has at least one solution in $$\left( {0,{\pi \over 2}} \right)$$ is .......
16
If the least and the largest real values of a, for which the
equation z + $$\alpha $$|z – 1| + 2i = 0 (z $$ \in $$ C and i = $$\sqrt { - 1} $$) has a solution, are p and q respectively; then 4(p2 + q2) is equal to __________.
17
$$\mathop {\lim }\limits_{n \to \infty } \tan \left\{ {\sum\limits_{r = 1}^n {{{\tan }^{ - 1}}\left( {{1 \over {1 + r + {r^2}}}} \right)} } \right\}$$ is equal to ______.
18
Let  A = {n $$ \in $$ N: n is a 3-digit number}

       B = {9k + 2: k $$ \in $$ N}

and C = {9k + $$l$$: k $$ \in $$ N} for some $$l ( 0 < l < 9)$$

If the sum of all the elements of the set A $$ \cap $$ (B $$ \cup $$ C) is 274 $$ \times $$ 400, then $$l$$ is equal to ________.
19
If one of the diameters of the circle x2 + y2 - 2x - 6y + 6 = 0 is a chord of another circle 'C', whose center is at (2, 1), then its radius is ________.
20
If $$\int\limits_{ - a}^a {\left( {\left| x \right| + \left| {x - 2} \right|} \right)} dx = 22$$, (a > 2) and [x] denotes the greatest integer $$ \le $$ x, then$$\int\limits_{ - a}^a {\left( {x + \left[ x \right]} \right)} dx$$ is equal to _________.
21
Let M be any 3 $$ \times $$ 3 matrix with entries from the set {0, 1, 2}. The maximum number of such matrices, for which the sum of diagonal elements of MTM is seven, is ________.
22
Let Bi (i = 1, 2, 3) be three independent events in a sample space. The probability that only B1 occur is $$\alpha $$, only B2 occurs is $$\beta $$ and only B3 occurs is $$\gamma $$. Let p be the probability that none of the events Bi occurs and these 4 probabilities satisfy the equations $$\left( {\alpha - 2\beta } \right)p = \alpha \beta $$ and $$\left( {\beta - 3\gamma } \right)p = 2\beta \gamma $$ (All the probabilities are assumed to lie in the interval (0, 1)).
Then $${{P\left( {{B_1}} \right)} \over {P\left( {{B_3}} \right)}}$$ is equal to ________.

Physics

1
A cube of side 'a' has point charges +Q located at each of its vertices except at the origin where the charge is $$-$$Q. The electric field at the centre of cube is :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Electrostatics Question 143 English
2
In the given figure, a mass M is attached to a horizontal spring which is fixed on one side to a rigid support. The spring constant of the spring is k. The mass oscillates on a frictionless surface with time period T and amplitude A. When the mass is in equilibrium position, as shown in the figure, another mass m is gently fixed upon it. The new amplitude of oscillations will be :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Simple Harmonic Motion Question 100 English
3
A current through a wire depends on time as

i = $$\alpha$$0t + $$\beta$$t2

where $$\alpha$$0 = 20 A/s and $$\beta$$ = 8 As$$-$$2. Find the charge crossed through a section of the wire in 15 s.
4
Match List I with List II.

List I List II
(a) Isothermal (i) Pressure constant
(b) Isochoric (ii) Temperature constant
(c) Adiabatic (iii) Volume constant
(d) Isobaric (iv) Heat content is constant

Choose the correct answer from the options given below :
5
n mole of a perfect gas undergoes a cyclic process ABCA (see figure) consisting of the following processes.

A $$ \to $$ B : Isothermal expansion at temperature T so that the volume is doubled from V1 to V2 = 2V1 and pressure charges from P1 to P2

B $$ \to $$ C : Isobaric compression at pressure P2 to initial volume V1.

C $$ \to $$ A : Isochoric change leading to change of pressure from P2 to P1.

Total workdone in the complete cycle ABCA is :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Heat and Thermodynamics Question 252 English
6
Each side of a box made of metal sheet in cubic shape is 'a' at room temperature 'T', the coefficient of linear expansion of the metal sheet is '$$\alpha$$'. The metal sheet is heated uniformly, by a small temperature $$\Delta$$T, so that its new temperature is T + $$\Delta$$T. Calculate the increase in the volume of the metal box.
7
A cell E1 of emf 6V and internal resistance 2$$\Omega$$ is connected with another cell E2 of emf 4V and internal resistance 8$$\Omega$$ (as shown in the figure). The potential difference across points X and Y is :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Current Electricity Question 206 English
8
The focal length f is related to the radius of curvature r of the spherical convex mirror by :
9
In a Young's double slit experiment, the width of the one of the slit is three times the other slit. The amplitude of the light coming from a slit is proportional to the slit-width. Find the ratio of the maximum to the minimum intensity in the interference pattern.
10
Four identical particles of equal masses 1 kg made to move along the circumference of a circle of radius 1 m under the action of their own mutual gravitational attraction. The speed of each particle will be :
11
Consider two satellites S1 and S2 with periods of revolution 1 hr. and 8 hr. respectively revolving around a planet in circular orbits. The ratio of angular velocity of satellite S1 to the angular velocity of satellite S2 is :
12
If Y, K and $$\eta $$ are the values of Young's modulus, bulk modulus and modulus of rigidity of any material respectively. Choose the correct relation for these parameters.
13
If the velocity-time graph has the shape AMB, what would be the shape of the corresponding acceleration-time graph?

JEE Main 2021 (Online) 24th February Morning Shift Physics - Motion in a Straight Line Question 75 English
14
In the given figure, the energy levels of hydrogen atom have been shown along with some transitions marked A, B, C, D and E.

The transitions A, B and C respectively represent :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Atoms and Nuclei Question 164 English
15
The work done by a gas molecule in an isolated system is

given by, $$W = \alpha {\beta ^2}{e^{ - {{{x^2}} \over {\alpha kT}}}}$$, where x is the displacement, k is the Boltzmann constant and T is the temperature. $$\alpha$$ and $$\beta$$ are constants. Then the dimensions of $$\beta$$ will be :
16
Two stars of masses m and 2m at a distance d rotate about their common centre of mass in free space. The period of revolution is :
17
Two equal capacitors are first connected in series and then in parallel. The ratio of the equivalent capacities in the two cases will be :
18
Moment of inertia (M. I.) of four bodies, having same mass and radius, are reported as;

I1 = M.I. of thin circular ring about its diameter,

I2 = M.I. of circular disc about an axis perpendicular to disc and going through the centre,

I3 = M.I. of solid cylinder about its axis and

I4 = M.I. of solid sphere about its diameter.

Then :
19
An unpolarised light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by 30$$^\circ$$ in clockwise direction, the intensity of emerging light will be _________ Lumens.
20
A ball with a speed of 9 m/s collides with another identical ball at rest. After the collision, the direction of each ball makes an angle of 30$$^\circ$$ with the original direction. The ratio of velocities of the balls after collision is x : y, where x is __________.
21
An electromagnetic wave of frequency 5 GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are 2. Its velocity in this medium is ____________ $$\times$$ 107 m/s.
22
A hydraulic press can lift 100 kg when a mass 'm' is placed on the smaller piston. It can lift ___________ kg when the diameter of the larger piston is increased by 4 times and that of the smaller piston is decreased by 4 times keeping the same mass 'm' on the smaller piston.
23
An inclined plane is bent in such a way that the vertical cross-section is given by $$y = {{{x^2}} \over 4}$$ where y is in vertical and x in horizontal direction. If the upper surface of this curved plane is rough with coefficient of friction $$\mu$$ = 0.5, the maximum height in cm at which a stationary block will not slip downward is _________ cm.
24
A common transistor radio set requires 12 V (D.C.) for its operation. The D.C. source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V (A.C.) on standard domestic A.C. supply. The number of turns of secondary coil are 24, then the number of turns of primary are ___________.
25
The coefficient of static friction between a wooden block of mass 0.5 kg and a vertical rough wall is 0.2. The magnitude of horizontal force that should be applied on the block to keep it adhere to the wall will be _________ N. [g = 10 ms$$-$$2]
26
In connection with the circuit drawn below, the value of current flowing through 2 k$$\Omega$$ resistor is _________ $$\times$$ 10$$-$$4 A.

JEE Main 2021 (Online) 24th February Morning Shift Physics - Semiconductor Question 129 English
27
Given below are two statements :

Statement I : Two photons having equal linear momenta have equal wavelengths.

Statement II : If the wavelength of photon is decreased, then the momentum and energy of a photon will also decrease.

In the light of the above statements, choose the correct answer from the options given below.
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