List of top Questions asked in JEE Main- 2021

When 3.00 g of a substance 'X' is dissolved in 100 g of \(\mathrm{CCl_4}\), it raises the boiling point by 0.60 K. The molar mass of the substance 'X' is ______________ g mol-1. (Nearest integer).

[Given \(K_b\) for \(\mathrm{CCl_4}\) is 5.0 K kg mol-1]
For a chemical reaction A \(\to\) B, it was found that concentration of B is increased by 0.2 mol L-1 in 30 min. The average rate of the reaction is ____________ \(\times 10^{-1}\) mol L-1 h-1. (in nearest integer)
An accelerated electron has a speed of \(5 \times 10^{6}\) ms-1 with an uncertainty of 0.02%. The uncertainty in finding its location while in motion is \(x \times 10^{-9}\) m. The value of x is ____________. (Nearest integer)

[Use mass of electron = \(9.1 \times 10^{-31}\) kg, h = \(6.63 \times 10^{-34}\) Js, \(\pi = 3.14\)]
Match List I with List II :
List-I
Example of colloids		List - II
Classification
(a) Cheese(i) dispersion of liquid in liquid
(b) Pumice stone(ii) dispersion of liquid in gas
(c) Hair cream(iii) dispersion of gas in solid
(d) Cloud(iv) dispersion of liquid in solid

Choose the most appropriate answer from the options given below
Given below are two statements :

Statement I : Chlorofluoro breakdown by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone.

Statement II : Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases, which add to the atmosphere.

For the above statements choose the correct answer from the options given below :
A system does 200 J of work and at the same time absorbs 150 J of heat. The magnitude of the change in internal energy is ____________ J. (Nearest integer)
Identify the process in which change in the oxidation state is five :
Which among the following is the strongest acid ?
Match List I with List II :
List-I
Elements		List-II
Properties
(a)Li(i)Poor water solubility of \(\mathrm{I^-}\) salt
(b)Na(ii)Most abundant element in cell fluid
(c)K(iii)Bicarbonate salt used in fire extinguisher
(d)Cs(iv)Carbonate salt decomposes easily on heating

Choose the correct answer from the options given below :
A biodegradable polyamide can be made from :
\(\mathrm{BrCH_2{-}CHO}\) \(\xrightarrow[\ \text{dry HCl gas}\ ]{\ \mathrm{EtOH\ excess}\ }\) "A" (major product) \(\xrightarrow{\ \mathrm{{}^tBuO^{-}K^{+}}\ }\) "B" (major product)

[where \(\mathrm{Et} \Rightarrow {-}\mathrm{C_2H_5}\), \(\mathrm{{}^tBu} \Rightarrow (\mathrm{CH_3})_3\mathrm{C{-}}\)]

Consider the above reaction sequence, Product "A" and Product "B" formed respectively are :
What is the major product "P" of the following reaction?
Which one of the following metals forms interstitial hydride easily?
Maleic anhydride can prepared by :
The spin only magnetic moments (in BM) for free \(\mathrm{Ti^{3+}}\), \(\mathrm{V^{2+}}\) and \(\mathrm{Sc^{3+}}\) ions respectively are :

(At.No. Sc : 21, Ti : 22, V : 23)
A reaction of benzonitrile with one equivalent \(\mathrm{CH_3MgBr}\) followed by hydrolysis produces a yellow liquid "P". The compound "P" will give positive ________.
Which one of the following is correct structure for cytosine?
Identify the species having one \(\pi\)-bond and maximum number of canonical forms from the following :
\(\mathrm{C_6H_5NO_2}\) \(\xrightarrow{\ \mathrm{Sn+HCl}\ }\) "A" \(\xrightarrow[\ \mathrm{H^{+}}\ ]{\ \mathrm{C_6H_5N_2^{+}Cl^{-}}\ }\) P (Yellow coloured Compound)

Consider the above reaction, the product "P" is :
The correct decreasing order of densities of the following compounds is :
The ionic radii of \(\mathrm{F^-}\) and \(\mathrm{O^{2-}}\) respectively are \(1.33\ \mathrm{\AA}\) and \(1.4\ \mathrm{\AA}\), while the covalent radius of N is \(0.74\ \mathrm{\AA}\).

The correct statement for the ionic radius of \(\mathrm{N^{3-}}\) from the following is :
Which one of the following metal complexes is most stable?
In the following the correct bond order sequence is :
In a semiconductor, the number density of intrinsic charge carries at \(27^\circ\mathrm{C}\) is \(1.5\times10^{16}/\mathrm{m^3}\). If the semiconductor is doped with impurity atom, the hole density increases to \(4.5\times10^{22}/\mathrm{m^3}\). The electron density in the doped semiconductor is ___________ \(\times 10^{9}/\mathrm{m^3}\).
A force of \(\vec F = (5y + 20)\,\hat{j}\ \mathrm{N}\) acts on a particle. The work done by this force when the particle is moved from \(y = 0\ \mathrm{m}\) to \(y = 10\ \mathrm{m}\) is ___________ J.