List of top Questions asked in JEE Main- 2021

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 \(\dots\dots\dots\).
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 \( \epsilon_0 = 8.8 \times 10^{-12} \, C^2 N^{-1} m^{-2} \))
In the structure of the dichromate ion, there is a :
Which one of the following \( 0.10 \, \text{M} \) aqueous solutions will exhibit the largest freezing point depression ?

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) 

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 :
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 :
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 :
The major component/ingredient of Portland Cement is :
The denticity of an organic ligand, biuret is :
BOD values (in ppm) for clean water (A) and polluted water (B) are expected respectively as :
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 :

Choose the correct name for compound given below : 

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 :

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

The major product formed in the following reaction is : 

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

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

Monomer of Novolac is :
Which one of the following compounds contains \(\beta\)-C\(_1\)-C\(_4\) glycosidic linkage?
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]
Ge (\(Z=32\)) in its ground state electronic configuration has \(x\) completely filled orbitals with \(m_l=0\). The value of \(x\) is \(\dots\dots\dots\).

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: \(x = 20\text{ kJ mol}^{-1}\), \(y = 45\text{ kJ mol}^{-1}\), \(z = 15\text{ kJ mol}^{-1}\)] 

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)
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 = \(96487\text{ C mol}^{-1}\)]