List of top Questions asked in JEE Main- 2021

Excess of isobutane on reaction with $Br_2$ in presence of light at $125^\circ C$ gives which one of the following, as the major product ?

The major product formed in the following reaction is :

Among the following compounds I-IV, which one forms a yellow precipitate on reacting sequentially with (i) NaOH (ii) dil. $HNO_3$ (iii) $AgNO_3$?

The major products formed in the following reaction sequence A and B are :

The correct options for the products A and B of the following reactions are :

The major product formed in the following reaction is :

The correct sequential addition of reagents in the preparation of 3-nitrobenzoic acid from benzene is :

The polymer formed on heating Novolac with formaldehyde is :

Given below are two statements :
Statement I : In the titration between strong acid and weak base methyl orange is suitable as an indicator.
Statement II : For titration of acetic acid with NaOH phenolphthalein is not a suitable indicator.
In the light of the above statements, choose the most appropriate answer from the options given below :

An aqueous KCl solution of density 1.20 g $mL^{-1}$ has a molality of 3.30 mol $kg^{-1}$. The molarity of the solution in mol $L^{-1}$ is _________. (Nearest integer)
[Molar mass of KCl = 74.5]

$AB_3$ is an interhalogen T-shaped molecule. The number of lone pairs of electrons on A is _________. (Integer answer)

The Born-Haber cycle for KCl is evaluated with the following data:
$\Delta_f H^\ominus$ for KCl = -436.7 kJ $mol^{-1}$; $\Delta_{sub} H^\ominus$ for K = 89.2 kJ $mol^{-1}$;
$\Delta_{ionization} H^\ominus$ for K = 419.0 kJ $mol^{-1}$; $\Delta_{electron gain} H^\ominus$ for $Cl_{(g)$ = -348.6 kJ $mol^{-1}$;
$\Delta_{bond} H^\ominus$ for $Cl_2$ = 243.0 kJ $mol^{-1}$.
The magnitude of lattice enthalpy of KCl in kJ $mol^{-1}$ is _________. (Nearest integer)}

Of the following four aqueous solutions, total number of those solutions whose freezing point is lower than that of 0.10 M $C_2H_5OH$ is _________. (Integer answer)
(i) 0.10 M $Ba_3(PO_4)_2$
(ii) 0.10 M $Na_2SO_4$
(iii) 0.10 M KCl
(iv) 0.10 M $Li_3PO_4$

The $OH^-$ concentration in a mixture of 5.0 mL of 0.0504 M $NH_4Cl$ and 2 mL of 0.0210 M $NH_3$ solution is $x \times 10^{-6}$ M. The value of $x$ is _________. (Nearest integer)
[Given $K_w = 1 \times 10^{-14}$ and $K_b = 1.8 \times 10^{-5}$]

The following data was obtained for chemical reaction given below at 975 K:

The order of the reaction with respect to NO is _________. (Integer answer)

These are physical properties of an element
(A) Sublimation enthalpy
(B) Ionisation enthalpy
(C) Hydration enthalpy
(D) Electron gain enthalpy
The total number of above properties that affect the reduction potential is _________. (Integer answer)

The number of 4f electrons in the ground state electronic configuration of $Gd^{2+}$ is _________. [Atomic number of Gd = 64] (Integer answer)

The ratio of number of water molecules in Mohr's salt and potash alum is _________ $\times 10^{-1}$. (Integer answer)

The total number of negative charge in the tetrapeptide, Gly-Glu-Asp-Tyr, at pH 12.5 will be _________. (Integer answer)

Out of all the patients in a hospital 89% are found to be suffering from heart ailment and 98% are suffering from lungs infection. If K% of them are suffering from both ailments, then K can not belong to the set :

The equation $\arg\left(\frac{z - 1}{z + 1}\right) = \frac{\pi}{4}$ represents a circle with :

If $ A = \begin{bmatrix} \frac{1}{\sqrt{5}} & \frac{2}{\sqrt{5}} \\ -\frac{2}{\sqrt{5}} & \frac{1}{\sqrt{5}} \end{bmatrix} $, $ B = \begin{bmatrix} 1 & 0 \\ i & 1 \end{bmatrix} $, $ i = \sqrt{-1} $, and $ Q = A^T B A $, then the inverse of the matrix $ A Q^{2021} A^T $ is equal to :