JEE Main 2021 August 31 Shift 1 Question Paper is available here with solutions PDF and detailed solutions for every question. NTA conducted the first shift on August 31, 2021, from 9:00 AM to 12:00 PM. The JEE Main 2021 Paper 1 (B.E./B.Tech) question paper includes the following:

  • 90 questions in a 3-hour CBT Mode: 30 each from Mathematics, Physics and Chemistry (75 to be attempted)
  • Section A: 20 multiple choice questions (MCQs) per subject, all compulsory, 4 marks each
  • Section B: 10 numerical value questions per subject, any 5 to be attempted, 4 marks each
  • Marking: +4 for a correct answer, -1 for an incorrect MCQ, 0 for an unattempted question; no negative marking for numerical value questions
  • Maximum marks: 300 (100 per subject)

JEE Main 2021 August 31 Shift 1 Question Paper with Solution PDF

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JEE Main 2021 August 31 Shift 1 Questions with Solutions


Mathematics - Section A (Q1 - Q20)

Question 1:

The number of real roots of the equation \( e^{4x} + 2e^{3x} - e^x - 6 = 0 \) is :

  • (1) 0
  • (2) 1
  • (3) 2
  • (4) 4

Question 2:

Let \(f\) be a non-negative function in \([0, 1]\) and twice differentiable in \((0, 1)\). If \(\int_0^x \sqrt{1 - (f'(t))^2} \, dt = \int_0^x f(t) \, dt\), \(0 \leq x \leq 1\) and \(f(0) = 0\), then \(\lim_{x \to 0} \frac{1}{x^2} \int_0^x f(t) \, dt\) :

  • (1) equals 0
  • (2) equals \(\frac{1}{2}\)
  • (3) equals 1
  • (4) does not exist

Question 3:

Let \(\vec{a}\) and \(\vec{b}\) be two vectors such that \(|2\vec{a} + 3\vec{b}| = |3\vec{a} + \vec{b}|\) and the angle between \(\vec{a}\) and \(\vec{b}\) is \(60^\circ\). If \(\frac{1}{8} \vec{a}\) is a unit vector, then \(|\vec{b}|\) is equal to :

  • (1) \(4\)
  • (2) \(5\)
  • (3) \(6\)
  • (4) \(8\)

Question 4:

The function \(f(x) = |x^2 - 2x - 3| \cdot e^{|9x^2 - 12x + 4|}\) is not differentiable at exactly :

  • (1) one point
  • (2) two points
  • (3) three points
  • (4) four points

Question 5:

Three numbers are in an increasing geometric progression with common ratio \( r \). If the middle number is doubled, then the new numbers are in an arithmetic progression with common difference \( d \). If the fourth term of GP is \( 3 r^2 \), then \( r^2 - d \) is equal to :

  • (1) \( 7 - 7\sqrt{3} \)
  • (2) \( 7 + \sqrt{3} \)
  • (3) \( 7 - \sqrt{3} \)
  • (4) \( 7 + 3\sqrt{3} \)

Question 6:

Which of the following is not correct for relation \( R \) on the set of real numbers?

  • (1) \( (x, y) \in R \iff |x - y| \leq 1 \) is reflexive and symmetric.
  • (2) \( (x, y) \in R \iff |x - |y|| \leq 1 \) is reflexive but not symmetric.
  • (3) \( (x, y) \in R \iff 0<|x - y| \leq 1 \) is neither transitive nor symmetric.
  • (4) \( (x, y) \in R \iff 0<|x - y| \leq 1 \) is symmetric and transitive.

Question 7:

The integral \(\int \frac{1}{\sqrt[4]{(x - 1)^3 (x + 2)^5}} \, dx\) is equal to :
(where C is a constant of integration)

  • (1) \(\frac{4}{3} \left( \frac{x - 1}{x + 2} \right)^{\frac{1}{4}} + C\)
  • (2) \(\frac{3}{4} \left( \frac{x + 2}{x - 1} \right)^{\frac{3}{4}} + C\)
  • (3) \(\frac{4}{3} \left( \frac{x - 1}{x + 2} \right)^{\frac{5}{4}} + C\)
  • (4) \(\frac{3}{4} \left( \frac{x + 2}{x - 1} \right)^{\frac{5}{4}} + C\)

Question 8:

If \(p\) and \(q\) are the lengths of the perpendiculars from the origin on the lines, \(x \csc \alpha - y \sec \alpha = k \cot 2\alpha\) and \(x \sin \alpha + y \cos \alpha = k \sin 2\alpha\) respectively, then \(k^2\) is equal to :

  • (1) \(p^2 + 2q^2\)
  • (2) \(p^2 + 4q^2\)
  • (3) \(2p^2 + q^2\)
  • (4) \(4p^2 + q^2\)

Question 9:

\(\csc 18^\circ\) is a root of the equation :

  • (1) \(x^2 - 2x - 4 = 0\)
  • (2) \(x^2 - 2x + 4 = 0\)
  • (3) \(x^2 + 2x - 4 = 0\)
  • (4) \(4x^2 + 2x - 1 = 0\)

Question 10:

If the following system of linear equations
\( 2x + y + z = 5 \)
\( x - y + z = 3 \)
\( x + y + az = b \)
has no solution, then :

  • (1) \( a = \frac{1}{3}, b \neq \frac{7}{3} \)
  • (2) \( a \neq \frac{1}{3}, b = \frac{7}{3} \)
  • (3) \( a = -\frac{1}{3}, b \neq \frac{7}{3} \)
  • (4) \( a \neq -\frac{1}{3}, b = \frac{7}{3} \)

Question 11:

The length of the latus rectum of a parabola, whose vertex and focus are on the positive \(x\)-axis at a distance \(R\) and \(S\) (\(S>R\)) respectively from the origin, is :

  • (1) \(2(S + R)\)
  • (2) \(2(S - R)\)
  • (3) \(4(S + R)\)
  • (4) \(4(S - R)\)

Question 12:

If the function 

is continuous at \(x = 0\), then \(\frac{1}{a} + \frac{1}{b} + \frac{4}{k}\) is equal to :} 
 

  • (1) \(-5\)
  • (2) \(5\)
  • (3) \(-4\)
  • (4) \(4\)

Question 13:

If \(\frac{dy}{dx} = \frac{2^{x+y} - 2^x}{2^y}\), \(y(0) = 1\), then \(y(1)\) is equal to :

  • (1) \(\log_2 (2 + e)\)
  • (2) \(\log_2 (2e)\)
  • (3) \(\log_2 (1 + e^2)\)
  • (4) \(\log_2 (1 + e)\)

Question 14:

\( \lim_{x \to 0} \frac{\sin^2(\pi \cos^4 x)}{x^4} \) is equal to :

  • (1) \( 2\pi^2 \)
  • (2) \( \pi^2 \)
  • (3) \( 4\pi^2 \)
  • (4) \( 4\pi \)

Question 15:

If \( a_r = \cos\frac{2r\pi}{9} + i \sin\frac{2r\pi}{9}, r = 1, 2, 3, \dots, i = \sqrt{-1} \), then the determinant \( \begin{vmatrix} a_1 & a_2 & a_3 \\ a_4 & a_5 & a_6 \\ a_7 & a_8 & a_9 \end{vmatrix} \) is equal to :

  • (1) \( a_9 \)
  • (2) \( a_1a_9 - a_3a_7 \)
  • (3) \( a_2a_6 - a_4a_8 \)
  • (4) \( a_5 \)

Question 16:

Let \(*, \square \in \{\wedge, \vee\}\) be such that the Boolean expression \((p * \sim q) \implies (p \square q)\) is a tautology. Then :

  • (1) \(* = \wedge, \square = \wedge\)
  • (2) \(* = \wedge, \square = \vee\)
  • (3) \(* = \vee, \square = \wedge\)
  • (4) \(* = \vee, \square = \vee\)

Question 17:

The sum of 10 terms of the series \( \frac{3}{1^2 \times 2^2} + \frac{5}{2^2 \times 3^2} + \frac{7}{3^2 \times 4^2} + \dots \) is :

  • (1) 1
  • (2) \( \frac{99}{100} \)
  • (3) \( \frac{120}{121} \)
  • (4) \( \frac{143}{144} \)

Question 18:

Let the equation of the plane, that passes through the point \((1, 4, -3)\) and contains the line of intersection of the planes \(3x - 2y + 4z - 7 = 0\) and \(x + 5y - 2z + 9 = 0\), be \(\alpha x + \beta y + \gamma z + 3 = 0\), then \(\alpha + \beta + \gamma\) is equal to :

  • (1) \(23\)
  • (2) \(15\)
  • (3) \(-15\)
  • (4) \(-23\)

Question 19:

A vertical pole fixed to the horizontal ground is divided in the ratio \(3 : 7\) by a mark on it with lower part shorter than the upper part. If the two parts subtend equal angles at a point on the ground \(18\text{ m}\) away from the base of the pole, then the height of the pole (in meters) is :

  • (1) \(12\sqrt{10}\)
  • (2) \(8\sqrt{10}\)
  • (3) \(6\sqrt{10}\)
  • (4) \(12\sqrt{15}\)

Question 20:

The line \(12x \cos \theta + 5y \sin \theta = 60\) is tangent to which of the following curves ?

  • (1) \(x^2 + y^2 = 60\)
  • (2) \(x^2 + y^2 = 169\)
  • (3) \(144x^2 + 25y^2 = 3600\)
  • (4) \(25x^2 + 12y^2 = 3600\)

Mathematics - Section B (Q21 - Q30)

Question 21:

Let \([t]\) denote the greatest integer \(\leq t\). Then the value of \(8 \cdot \int_{-1/2}^{1} ([2x] + |x|) \, dx\) is _________
 


Question 22:

A point \(z\) moves in the complex plane such that \(\arg\left(\frac{z-2}{z+2}\right) = \frac{\pi}{4}\), then the minimum value of \(|z - 9\sqrt{2} - 2i|^2\) is equal to _________


Question 23:

If 'R' is the least value of 'a' such that the function \(f(x) = x^2 + ax + 1\) is increasing on \([1, 2]\) and 'S' is the greatest value of 'a' such that the function \(f(x) = x^2 + ax + 1\) is decreasing on \([1, 2]\), then the value of \(|R-S|\) is ________________.


Question 24:

The mean of 10 numbers \(7 \times 8, 10 \times 10, 13 \times 12, 16 \times 14, \dots\) is ___________
 


Question 25:

If the variable line \(3x + 4y = \alpha\) lies between the two circles \((x-1)^2 + (y-1)^2 = 1\) and \((x-9)^2 + (y-1)^2 = 4\), without intercepting a chord on either circle, then the sum of all the integral values of \(\alpha\) is _____________
 


Question 26:

The number of six letter words (with or without meaning), formed using all the letters of the word 'VOWELS', so that all the consonants never come together, is ___________
 


Question 27:

If \(x \phi(x) = \int_{5}^{x} (3t^2 - 2\phi'(t))dt\), \(x>-2\), and \(\phi(0)=4\), then \(\phi(2)\) is ___________


Question 28:

If \(\left(\frac{3^6}{4^4}\right)k\) is the term independent of \(x\) in the binomial expansion of \(\left(\frac{x}{4} - \frac{12}{x^2}\right)^{12}\), then \(k\) is equal to ___________
 


Question 29:

An electric instrument consists of two units. Each unit must function independently for the instrument to operate. The probability that the first unit functions is \(0.9\) and that of the second unit is \(0.8\). The instrument is switched on and it fails to operate. If the probability that only the first unit failed and second unit is functioning is \(p\), then \(98p\) is equal to ________________.


Question 30:

The square of the distance of the point of intersection of the line \(\frac{x-1}{2} = \frac{y-2}{3} = \frac{z+1}{6}\) and the plane \(2x - y + z = 6\) from the point \((-1, -1, 2)\) is _____________
 


Physics - Section A (Q31 - Q50)

Question 31:

A helicopter is flying horizontally with a speed 'v' at an altitude 'h' has to drop a food packet for a man on the ground. What is the distance of helicopter from the man when the food packet is dropped ?

  • (1) \(\sqrt{\frac{2gh}{v^2} + h^2}\)
  • (2) \(\sqrt{\frac{2v^2h}{g} + h^2}\)
  • (3) \(\sqrt{2ghv^2 + h^2}\)
  • (4) \(\sqrt{\frac{2ghv^2 + 1}{h^2}}\)

Question 32:

In the following logic circuit the sequence of the inputs A, B are (0, 0), (0, 1), (1, 0) and (1, 1). The output Y for this sequence will be : 

  • (1) 1, 1, 1, 0
  • (2) 1, 0, 1, 0
  • (3) 0, 1, 0, 1
  • (4) 0, 0, 1, 1

Question 33:

Two particles A and B having charges \(20\,\mu C\) and \(-5\,\mu C\) respectively are held fixed with a separation of \(5\,\text{cm}\). At what position a third charged particle should be placed so that it does not experience a net electric force ?

  • (1) At midpoint between two charges
  • (2) At \(5\,\text{cm}\) from \(-5\,\mu C\) on the right side
  • (3) At \(5\,\text{cm}\) from \(20\,\mu C\) on the left side of system
  • (4) At \(1.25\,\text{cm}\) from a \(-5\,\mu C\) between two charges

Question 34:

An object is placed at the focus of concave lens having focal length f. What is the magnification and distance of the image from the optical centre of the lens ?

  • (1) Very high, \( \infty \)
  • (2) 1, \( \infty \)
  • (3) \( \frac{1}{2}, \frac{f}{2} \)
  • (4) \( \frac{1}{4}, \frac{f}{4} \)

Question 35:

A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at centre, when a current I passes through coil :

  • (1) \(\frac{\mu_0 IN}{2(b - a)} \log_e \left(\frac{b}{a}\right)\)
  • (2) \(\frac{\mu_0 I}{8} \left(\frac{a - b}{a + b}\right)\)
  • (3) \(\frac{\mu_0 I}{4(a - b)} \left[\frac{1}{a} - \frac{1}{b}\right]\)
  • (4) \(\frac{\mu_0 I}{8} \left[\frac{a + b}{a - b}\right]\)

Question 36:

A body of mass M moving at speed \(V_0\) collides elastically with a mass 'm' at rest. After the collision, the two masses move at angles \(\theta_1\) and \(\theta_2\) with respect to the initial direction of motion of the body of mass M. The largest possible value of the ratio M/m, for which the angles \(\theta_1\) and \(\theta_2\) will be equal, is :

  • (1) 2
  • (2) 3
  • (3) 1
  • (4) 4

Question 37:

The masses and radii of the earth and moon are (\(M_1, R_1\)) and (\(M_2, R_2\)) respectively. Their centres are at a distance 'r' apart. Find the minimum escape velocity for a particle of mass 'm' to be projected from the middle of these two masses :

  • (1) \(V = \frac{\sqrt{2G(M_1 + M_2)}}{r}\)
  • (2) \(V = \frac{1}{2} \sqrt{\frac{2G(M_1 + M_2)}{r}}\)
  • (3) \(V = \sqrt{\frac{4G(M_1 + M_2)}{r}}\)
  • (4) \(V = \frac{1}{2} \sqrt{\frac{4G(M_1 + M_2)}{r}}\)

Question 38:

A small square loop of side 'a' and one turn is placed inside a larger square loop of side b and one turn (\( b \gg a \)). The two loops are coplanar with their centres coinciding. If a current I is passed in the square loop of side 'b', then the coefficient of mutual inductance between the two loops is :

  • (1) \( \frac{\mu_0}{4\pi} \frac{8\sqrt{2} a^2}{b} \)
  • (2) \( \frac{\mu_0}{4\pi} \frac{8\sqrt{2} b^2}{a} \)
  • (3) \( \frac{\mu_0}{4\pi} \frac{8\sqrt{2}}{a} \)
  • (4) \( \frac{\mu_0}{4\pi} \frac{8\sqrt{2}}{b} \)

Question 39:

Choose the correct waveform that can represent the voltage across R of the following circuit, assuming the diode is ideal one : 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 40:

A uniform heavy rod of weight \(10\,\text{kg}\,\text{ms}^{-2}\), cross-sectional area \(100\,\text{cm}^2\) and length \(20\,\text{cm}\) is hanging from a fixed support. Young modulus of the material of the rod is \(2 \times 10^{11}\,\text{Nm}^{-2}\). Neglecting the lateral contraction, find the elongation of rod due to its own weight :

  • (1) \(2 \times 10^{-9}\,\text{m}\)
  • (2) \(5 \times 10^{-10}\,\text{m}\)
  • (3) \(5 \times 10^{-8}\,\text{m}\)
  • (4) \(4 \times 10^{-8}\,\text{m}\)

Question 41:

Two plane mirrors \( M_1 \) and \( M_2 \) are at right angle to each other shown. A point source 'P' is placed at 'a' and '2a' meter away from \( M_1 \) and \( M_2 \) respectively. The shortest distance between the images thus formed is : (Take \( \sqrt{5} = 2.3 \)) 

  • (1) \( 3a \)
  • (2) \( 4.6a \)
  • (3) \( 2\sqrt{10} a \)
  • (4) \( 2.3a \)

Question 42:

Match List - I with List - II 

Choose the most appropriate answer from the option given below : 
 

  • (1) (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
  • (2) (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
  • (3) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
  • (4) (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

Question 43:

For an ideal gas the instantaneous change in pressure 'p' with volume 'v' is given by the equation \(\frac{dp}{dv} = -ap\). If \(p = p_0\) at \(v = 0\) is the given boundary condition, then the maximum temperature one mole of gas can attain is : (Here R is the gas constant)

  • (1) \(0^\circ\text{C}\)
  • (2) \(\frac{p_0}{aeR}\)
  • (3) \(\frac{ap_0}{eR}\)
  • (4) infinity

Question 44:

Which of the following equations is dimensionally incorrect ?
Where t = time, h = height, s = surface tension, \(\theta\) = angle, \(\rho\) = density, a, r = radius, g = acceleration due to gravity, v = volume, p = pressure, W = work done, \(\Gamma\) = torque, \(\epsilon\) = permittivity, E = electric field, J = current density, L = length.

  • (1) \(h = \frac{2s \cos\theta}{\rho rg}\)
  • (2) \(v = \frac{\pi pa^4}{8\eta L}\)
  • (3) \(W = \Gamma \theta\)
  • (4) \(J = \epsilon \frac{\partial E}{\partial t}\)

Question 45:

Angular momentum of a single particle moving with constant speed along circular path :

  • (1) is zero
  • (2) remains same in magnitude but changes in the direction
  • (3) changes in magnitude but remains same in the direction
  • (4) remains same in magnitude and direction

Question 46:

In an ac circuit, an inductor, a capacitor and a resistor are connected in series with \( X_L = R = X_C \). Impedance of this circuit is :

  • (1) Zero
  • (2) \( R\sqrt{2} \)
  • (3) \( R \)
  • (4) \( 2R^2 \)

Question 47:

A moving proton and electron have the same de-Broglie wavelength. If K and P denote the K.E. and momentum respectively. Then choose the correct option :

  • (1) \( K_p = K_e \) and \( P_p = P_e \)
  • (2) \( K_p>K_e \) and \( P_p = P_e \)
  • (3) \( K_p<K_e \) and \( P_p = P_e \)
  • (4) \( K_p<K_e \) and \( P_p<P_e \)

Question 48:

Consider a galvanometer shunted with \( 5 \Omega \) resistance and \( 2% \) of current passes through it. What is the resistance of the given galvanometer ?

  • (1) \( 300 \Omega \)
  • (2) \( 245 \Omega \)
  • (3) \( 344 \Omega \)
  • (4) \( 226 \Omega \)

Question 49:

A reversible engine has an efficiency of \(\frac{1}{4}\). If the temperature of the sink is reduced by \(58^\circ\text{C}\), its efficiency becomes double. Calculate the temperature of the sink :

  • (1) \(280^\circ\text{C}\)
  • (2) \(382^\circ\text{C}\)
  • (3) \(180.4^\circ\text{C}\)
  • (4) \(174^\circ\text{C}\)

Question 50:

A sample of a radioactive nucleus A disintegrates to another radioactive nucleus B, which in turn disintegrates to some other stable nucleus C. Plot of a graph showing the variation of number of atoms of nucleus B versus time is : (Assume that at t=0, there are no B atoms in the sample) 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Physics - Section B (Q51 - Q60)

Question 51:

When a rubber ball is taken to a depth of \(\dots\dots\dots\) m in deep sea, its volume decreases by \( 0.5% \).
(The bulk modulus of rubber \(= 9.8 \times 10^8 \, Nm^{-2} \)
Density of sea water \(= 10^3 \, kg m^{-3} \)
\( g = 9.8 \, m/s^2 \))


Question 52:

A particle of mass \( 1 \, kg \) is hanging from a spring of force constant \( 100 \, Nm^{-1} \). The mass is pulled slightly downward and released so that it executes free simple harmonic motion with time period T. The time when the kinetic energy and potential energy of the system will become equal, is \( \frac{T}{x} \). The value of x is \(\dots\dots\dots\).


Question 53:

A square shaped wire with resistance of each side \( 3 \, \Omega \) is bent to form a complete circle. The resistance between two diametrically opposite points of the circle in unit of \( \Omega \) will be \(\dots\dots\dots\).


Question 54:

A wire having a linear mass density \( 9.0 \times 10^{-4} \, kg/m \) is stretched between two rigid supports with a tension of \( 900 \, N \). The wire resonates at a frequency of \( 500 \, Hz \). The next higher frequency at which the same wire resonates is \( 550 \, Hz \). The length of the wire is \(\dots\dots\dots\) m.


Question 55:

The voltage drop across \( 15 \, \Omega \) resistance in the given figure will be \(\dots\dots\) V. 


Question 56:

A block moving horizontally on a smooth surface with a speed of \( 40 \, ms^{-1} \) splits into two equal parts. If one of the parts moves at \( 60 \, ms^{-1} \) in the same direction, then the fractional change in the kinetic energy will be \( x : 4 \) where \( x = \dots\dots\dots \).


Question 57:

The electric field in an electromagnetic wave is given by \( E = (50 \, NC^{-1}) \sin \omega (t - x/c) \). The energy contained in a cylinder of volume V is \( 5.5 \times 10^{-12} \, J \). The value of V is \(\dots\dots\dots\) \( cm^3 \).
(given \( \epsilon_0 = 8.8 \times 10^{-12} \, C^2 N^{-1} m^{-2} \))


Question 58:

A capacitor of \( 50 \, \mu F \) is connected in a circuit as shown in figure. The charge on the upper plate of the capacitor is \(\dots\dots\dots\) \( \mu C \). 


Question 59:

A car is moving on a plane inclined at \( 30^\circ \) to the horizontal with an acceleration of \( 10 \, ms^{-2} \) parallel to the plane upward. A bob is suspended by a string from the roof of the car. The angle in degrees which the string makes with the vertical is \(\dots\dots\dots\). (Take \( g = 10 \, ms^{-2} \))


Question 60:

If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at \( 160 \, m \), then the maximum range of LOS communication is \(\dots\dots\dots\) km.
(Take radius of Earth \( = 6400 \, km \))


Chemistry - Section A (Q61 - Q80)

Question 61:

The correct order of reactivity of the given chlorides with acetate in acetic acid is : 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 62:

In the structure of the dichromate ion, there is a :

  • (1) linear symmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
  • (2) linear unsymmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
  • (3) non-linear symmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
  • (4) non-linear unsymmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.

Question 63:

Which one of the following compounds contains \(\beta\)-C\(_1\)-C\(_4\) glycosidic linkage?

  • (1) Lactose
  • (2) Amylose
  • (3) Sucrose
  • (4) Maltose

Question 64:

The major products A and B in the following set of reactions are : 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 65:

Which one of the following lanthanides exhibits +2 oxidation state with diamagnetic nature ? (Given Z for Nd=60, Yb=70, La=57, Ce=58)

  • (1) Nd
  • (2) Yb
  • (3) La
  • (4) Ce

Question 66:

The major product formed in the following reaction is : 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 67:

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Treatment of bromine water with propene yields 1-bromopropan-2-ol.
Reason (R) : Attack of water on bromonium ion follows Markovnikov rule and results in 1-bromopropan-2-ol.
In the light of the above statements, choose the most appropriate answer from the options given below :

  • (1) Both (A) and (R) are true and (R) is the correct explanation of (A).
  • (2) Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
  • (3) (A) is true but (R) is false.
  • (4) (A) is false but (R) is true.

Question 68:

The denticity of an organic ligand, biuret is :

  • (1) 2
  • (2) 4
  • (3) 6
  • (4) 3

Question 69:

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Metallic character decreases and non-metallic character increases on moving from left to right in a period.
Reason (R) : It is due to increase in ionisation enthalpy and decrease in electron gain enthalpy, when one moves from left to right in a period.
In the light of the above statements, choose the most appropriate answer from the options given below :

  • (1) Both (A) and (R) are correct and (R) is the correct explanation of (A).
  • (2) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
  • (3) (A) is true but (R) is false.
  • (4) (A) is false but (R) is true.

Question 70:

Choose the correct name for compound given below : 

  • (1) (4E)-5-Bromo-hex-4-en-2-yne
  • (2) (2E)-2-Bromo-hex-2-en-4-yne
  • (3) (2E)-2-Bromo-hex-4-yn-2-ene
  • (4) (4E)-5-Bromo-hex-2-en-4-yne

Question 71:

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : A simple distillation can be used to separate a mixture of propanol and propanone.
Reason (R) : Two liquids with a difference of more than \( 20^\circ\text{C} \) in their boiling points can be separated by simple distillations.
In the light of the above statements, choose the most appropriate answer from the options given below :

  • (1) Both (A) and (R) are correct and (R) is the correct explanation of (A).
  • (2) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
  • (3) (A) is true but (R) is false.
  • (4) (A) is false but (R) is true.

Question 72:

Which one of the following \( 0.10 \, \text{M} \) aqueous solutions will exhibit the largest freezing point depression ?

  • (1) glycine
  • (2) glucose
  • (3) \( \text{KHSO}_4 \)
  • (4) hydrazine

Question 73:

The structure of product C, formed by the following sequence of reactions is : 
\( CH_3COOH + SOCl_2 \to A \xrightarrow[\text{AlCl}_3]{\text{Benzene}} B \xrightarrow[\text{}^-OH]{\text{KCN}} C \) 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 74:

Select the graph that correctly describes the adsorption isotherms at two temperatures \( T_1 \) and \( T_2 \) (\( T_1>T_2 \)) for a gas : (x - mass of the gas adsorbed, m - mass of adsorbent, P - pressure) 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 75:

The major component/ingredient of Portland Cement is :

  • (1) tricalcium aluminate
  • (2) dicalcium aluminate
  • (3) tricalcium silicate
  • (4) dicalcium silicate

Question 76:

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Aluminium is extracted from bauxite by the electrolysis of molten mixture of \( \text{Al}_2\text{O}_3 \) with cryolite.
Reason (R) : The oxidation state of Al in cryolite is +3.
In the light of the above statements, choose the most appropriate answer from the options given below :

  • (1) Both (A) and (R) are correct and (R) is the correct explanation of (A).
  • (2) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
  • (3) (A) is true but (R) is false.
  • (4) (A) is false but (R) is true.

Question 77:

Monomer of Novolac is :

  • (1) \(o\)-Hydroxymethylphenol.
  • (2) phenol and melamine.
  • (3) 1,3-Butadiene and styrene.
  • (4) 3-Hydroxybutanoic acid.

Question 78:

Given below are two statements :
Statement I : The process of producing syn-gas is called gasification of coal.
Statement II : The composition of syn-gas is \( \text{CO} + \text{CO}_2 + \text{H}_2 \) (1 : 1 : 1).
In the light of the above statements, choose the most appropriate answer from the options given below :

  • (1) Both Statement I and Statement II are true.
  • (2) Both Statement I and Statement II are false.
  • (3) Statement I is true but Statement II is false.
  • (4) Statement I is false but Statement II is true.

Question 79:

Which one of the following is the correct PV vs P plot at constant temperature for an ideal gas ? (P and V stand for pressure and volume of the gas respectively) 

  • (1) A
  • (2) B
  • (3) C
  • (4) D

Question 80:

BOD values (in ppm) for clean water (A) and polluted water (B) are expected respectively as :

  • (1) \( A>15, B>47 \)
  • (2) \( A<5, B>17 \)
  • (3) \( A>50, B<27 \)
  • (4) \( A>25, B<17 \)

Chemistry - Section B (Q81 - Q90)

Question 81:

Consider the following cell reaction
\(\text{Cd}_{(s)} + \text{Hg}_2\text{SO}_{4(s)} + \frac{9}{5} \text{H}_2\text{O}_{(l)} \rightleftharpoons \text{CdSO}_4 \cdot \frac{9}{5} \text{H}_2\text{O}_{(s)} + 2\text{Hg}_{(l)}\)
The value of \(E_{cell}^0\) is \(4.315\text{ V}\) at \(25^\circ\text{C}\). If \(\Delta H^0 = -825.2\text{ kJ mol}^{-1}\), the standard entropy change \(\Delta S^0\) in J K\(^{-1}\) is \(\dots\dots\dots\). (Nearest integer)
[Given : Faraday constant = \(96487\text{ C mol}^{-1}\)]


Question 82:

The molarity of the solution prepared by dissolving \(6.3\text{ g}\) of oxalic acid (\(\text{H}_2\text{C}_2\text{O}_4 \cdot 2\text{H}_2\text{O}\)) in \(250\text{ mL}\) of water in mol L\(^{-1}\) is \(x \times 10^{-2}\). The value of \(x\) is \(\dots\dots\dots\). (Nearest integer)
[Atomic mass : H : 1.0, C : 12.0, O : 16.0]


Question 83:

The total number of reagents from those given below, that can convert nitrobenzene into aniline is ___________. (Integer answer) 
I. \( Sn - HCl \) 
II. \( Sn - NH_4OH \) 
III. \( Fe - HCl \) 
IV. \( Zn - HCl \) 
V. \( H_2 - Pd \) 
VI. \( H_2 - Raney \ Nickel \)} 
 


Question 84:

For a first order reaction, the ratio of the time for \(75%\) completion of a reaction to the time for \(50%\) completion is \(\dots\dots\dots\). (Integer answer)


Question 85:

The number of hydrogen bonded water molecule(s) associated with stoichiometry \( CuSO_4 \cdot 5H_2O \) is ____________
 


Question 86:

According to the following figure, the magnitude of the enthalpy change of the reaction \(A + B \to M + N\) in kJ mol\(^{-1}\) is equal to \(\dots\dots\dots\). (Integer answer) 
[Given: \(x = 20\text{ kJ mol}^{-1}\), \(y = 45\text{ kJ mol}^{-1}\), \(z = 15\text{ kJ mol}^{-1}\)] 


Question 87:

Ge (\(Z=32\)) in its ground state electronic configuration has \(x\) completely filled orbitals with \(m_l=0\). The value of \(x\) is \(\dots\dots\dots\).


Question 88:

A\(_3\)B\(_2\) is a sparingly soluble salt of molar mass M (g mol\(^{-1}\)) and solubility \(x\text{ g L}^{-1}\). The solubility product satisfies \(K_{sp} = a \left(\frac{x}{M}\right)^5\). The value of \(a\) is \(\dots\dots\dots\). (Integer answer)


Question 89:

Consider the sulphides \( HgS, PbS, CuS, Sb_2S_3, As_2S_3 \) and \( CdS \). Number of these sulphides soluble in \( 50% \ HNO_3 \) is _____________ 
 


Question 90:

The number of halogen/(s) forming halic (V) acid is ____________
 

JEE Main 2021 Exam Pattern and Marking Scheme

ParticularsDetails
Exam ModeOnline (Computer-Based Test)
PaperB.E./B.Tech (Paper 1)
Duration3 hours (180 minutes)
Type of QuestionsMultiple Choice Questions (MCQs) + Numerical Value Questions
SubjectsMathematics, Physics, Chemistry
Total Questions90 questions (75 to be attempted)
Total Marks300 marks
Marking Scheme+4 for correct answer & -1 for incorrect MCQ; no negative marking for Numerical Value Questions

JEE Main 2021 August 31 Shift 1 Difficulty Level

JEE Main Question Paper for August 31, 2021, Forenoon Session was termed to be of moderate difficulty by the experts. According to the test-takers, the Physics section was the most difficult section of the paper. Second on the difficulty scale was the Mathematics Section. The Chemistry section was the easiest of the three sections. In keeping with JEE Main Exam Pattern, each section featured 30 questions (20 MCQs and 10 NATs), with the option of attempting any 5 NAT questions for a total of 25 attempts by the candidates.

JEE Main 2021 B.E./B.Tech Question Paper August 31 (FN): Paper Analysis

JEE Main August 31, 2021 Forenoon (Shift 1) was conducted from 9.00 AM to 12.00 Noon. The sectional analysis of the paper is as follows:

Mathematics

  • Differential Calculus (12%), Integral Calculus (18%), Coordinate Geometry (12%), and Trigonometry (15%) were the major contributing units in the paper
  • The questions asked from Class XI and Class XII topics were roughly equal. Around 16 questions were asked from class XII topics and 14 Questions were asked from class XI topics. View JEE Main Mathematics Syllabus

Physics

  • Mechanics (37%), Electrodynamics(27%), and Modern Physics (17%) were the major units asked in the paper.
  • 19 questions were asked from class XII topics and 11 Questions were asked from class XI topics. View JEE Main Physics syllabus

Chemistry

  • Dominant units in the paper included: Organic Chemistry II (36%), Inorganic Chemistry I (20%), and Physical Chemistry II (20%)
  • 13 Questions were framed from Class XI Chemistry Syllabus, and 17 Questions were framed from Class XII Chemistry Syllabus. View JEE Main Chemistry Syllabus