List of top Questions asked in JEE Main- 2021

The addition of dilute NaOH to Cr\(^{3+}\) salt solution will give :

100 g of propane is completely reacted with 1000 g of oxygen. The mole fraction of carbon dioxide in the resulting mixture is \(x \times 10^{-2}\). The value of x is _________. (Nearest integer)
[Atomic weight : H=1.008; C=12.00; O=16.00]

Two flasks I and II shown below are connected by a valve of negligible volume. When the valve is opened, the final pressure of the system in bar is \(x \times 10^{-2}\). The value of x is _________. (Integer answer)
[Assume - Ideal gas; 1 bar = 10\(^5\) Pa; Molar mass of N\(_2\) = 28.0 g mol\(^{-1}\); R=8.31 J mol\(^{-1}\) K\(^{-1}\)]

The number of photons emitted by a monochromatic (single frequency) infrared range finder of power 1 mW and wavelength of 1000 nm, in 0.1 second is \(x \times 10^{13}\). The value of x is _________. (Nearest integer)
(h = 6.63 \(\times\) 10\(^{-34}\) Js, c=3.00 \(\times\) 10\(^8\) ms\(^{-1}\))

The number of species having non-pyramidal shape among the following is _________.
(A) SO\(_3\)
(B) NO\(_3^-\)
(C) PCl\(_3\)
(D) CO\(_3^{2-}\)

Data given for the following reaction is as follows:
FeO(s) + C(graphite) \(\rightarrow\) Fe(s) + CO(g)
The minimum temperature in K at which the reaction becomes spontaneous is _________. (Integer answer)

40 g of glucose (Molar mass = 180) is mixed with 200 mL of water. The freezing point of solution is _________ K. (Nearest integer)
[Given: K\(_f\)= 1.86 K kg mol\(^{-1}\); Density of water=1.00 g cm\(^{-3}\); Freezing point of water = 273.15 K]

When 5.1 g of solid NH\(_4\)HS is introduced into a two litre evacuated flask at 27\(^\circ\)C, 20% of the solid decomposes into gaseous ammonia and hydrogen sulphide. The K\(_p\) for the reaction at 27\(^\circ\)C is \(x \times 10^{-2}\). The value of x is _________. (Integer answer)
[Given R = 0.082 L atm K\(^{-1}\) mol\(^{-1}\)]

The resistance of a conductivity cell with cell constant 1.14 cm\(^{-1}\), containing 0.001 M KCl at 298 K is 1500 \(\Omega\). The molar conductivity of 0.001 M KCl solution at 298 K in S cm\(^2\) mol\(^{-1}\) is _________. (Integer answer)

The first order rate constant for the decomposition of CaCO\(_3\) at 700 K is 6.36 \(\times\) 10\(^{-3}\) s\(^{-1}\) and activation energy is 209 kJ mol\(^{-1}\). Its rate constant (in s\(^{-1}\)) at 600 K is \(x \times 10^{-6}\). The value of x is _________. (Nearest integer)
[Given R = 8.31 J K\(^{-1}\) mol\(^{-1}\); log 6.36\(\times\)10\(^{-3}\)=\(-2.19\), 10\(^{-4.79}\)=1.62\(\times\)10\(^{-5}\)]

The number of optical isomers possible for [Cr(C\(_2\)O\(_4\))\(_3\)]\(^{3-}\) is _________.

The set of all values of k \(>\) -1, for which the equation
(3x\(^2\)+4x+3)\(^2\) - (k+1)(3x\(^2\)+4x+3)(3x\(^2\)+4x+2) + k(3x\(^2\)+4x+2)\(^2\) = 0 has real roots, is :

Let [\(\lambda\)] be the greatest integer less than or equal to \(\lambda\). The set of all values of \(\lambda\) for which the system of linear equations x+y+z=4, 3x+2y+5z=3, 9x + 4y + (28 + [\(\lambda\)])z = [\(\lambda\)] has a solution is :

Let \( A = \begin{pmatrix} \lfloor x+1 \rfloor & \lfloor x+2 \rfloor & \lfloor x+3 \rfloor \\ \lfloor x \rfloor & \lfloor x+3 \rfloor & \lfloor x+3 \rfloor \\ \lfloor x \rfloor & \lfloor x+2 \rfloor & \lfloor x+4 \rfloor \end{pmatrix} \), where \( \lfloor t \rfloor \) denotes the greatest integer less than or equal to \( t \). If \( \det(A) = 192 \), then the set of values of \( x \) is the interval:

If 0 \(<\) x \(<\) 1 and y = \(\frac{1}{2}x^2 + \frac{2}{3}x^3 + \frac{3}{4}x^4 + ...\), then the value of e\(^{1+y}\) at x = \(\frac{1}{2}\) is :

If \( \lim_{x \to \infty} (\sqrt{x^2 - x + 1} - ax) = b \), then the ordered pair (a, b) is :

If \(y(x) = \cot^{-1}\left(\frac{\sqrt{1 + \sin x} + \sqrt{1 - \sin x}}{\sqrt{1 + \sin x} - \sqrt{1 - \sin x}}\right), x \in \left(\frac{\pi}{2}, \pi\right)\), then \(\frac{dy}{dx}\) at \(x = \frac{5\pi}{6}\) is :

A box open from top is made from a rectangular sheet of dimension a \(\times\) b by cutting squares each of side x from each of the four corners and folding up the flaps. If the volume of the box is maximum, then x is equal to:

The area of the region bounded by the parabola \((y-2)^2 = (x-1)\), the tangent to it at the point whose ordinate is 3 and the x-axis is :

Let A(a, 0), B(b, 2b + 1) and C(0, b), b \(\neq\) 0, |b| \(\neq\) 1, be points such that the area of triangle ABC is 1 sq. unit, then the sum of all possible values of a is :

If two tangents drawn from a point P to the parabola \(y^2 = 16(x-3)\) are at right angles, then the locus of point P is :

Each of the persons A and B independently tosses three fair coins. The probability that both of them get the same number of heads is :

The Boolean expression \((p \land q) \Rightarrow ((r \land q) \land p)\) is equivalent to :

Let \(z_1\) and \(z_2\) be two complex numbers such that \( \arg(z_1 - z_2) = \frac{\pi}{4} \) and \(z_1, z_2\) satisfy the equation \(|z-3| = \text{Re}(z)\). Then the imaginary part of \(z_1+z_2\) is equal to _________.

Let S = 1, 2, 3, 4, 5, 6, 9. Then the number of elements in the set T={A \(\subseteq\) S: A \(\neq \emptyset\) and the sum of all the elements of A is not a multiple of 3} is _________.