List of top Questions asked in JEE Main- 2021

Monomer of Novolac is :
The correct shape and I-I-I bond angles respectively in $I_3^-$ ion are :
The correct set from the following in which both pairs are in correct order of melting point is :
Which one of the following compounds contains \(\beta\)-C\(_1\)-C\(_4\) glycosidic linkage?
The statements that are TRUE : (A) methane leads to both global warming and photochemical smog (B) methane is generated from paddy fields (C) methane is a stronger global warming gas than CO₂ (D) methane is a part of reducing smog. Choose the most appropriate answer from the options given below :
Match List - I with List - II : List - I (Process)
(a) Deacon's process
(b) Contact process
(c) Cracking of hydrocarbons
(d) Hydrogenation of vegetable oils List - II (Catalyst)
(i) ZSM-5
(ii) CuCl₂
(iii) Particles 'Ni'
(iv) V₂O₅
The major product (A) formed in the reaction given below is :
\includegraphics[width=0.6\linewidth]{image43.png}
The solubility of Ca(OH)$_2$ in water is:
[Given: The solubility product of Ca(OH)$_2$ in water = 5.5 $\times$ 10⁻⁶]

The diazonium salt of which of the following compounds will form a coloured dye on reaction with β-Naphthol in NaOH ? 

Statements about heavy water are given below A. Heavy water is used in exchange reactions for the study of reaction mechanisms B. Heavy water is prepared by exhaustive electrolysis of water C. Heavy water has higher boiling point than ordinary water D. Viscosity of $H _{2} O$ is greater than $D _{2} O$
Match List - I and List - II. List - I : (a) R-COCl $\to$ R-CHO (b) R-CH2-COOH $\to$ R-CH-Cl-COOH (c) R-CONH2 $\to$ R-NH2 (d) R-COCH3 $\to$ R-CH2-CH3 List - II : (i) Br2/NaOH (ii) H2/Pd-BaSO4 (iii) Zn(Hg)/Conc. HCl (iv) Cl2/Red P, H2O

Which one of the following compounds is not aromatic ? 

The parameters of the unit cell of a substance are a = 2.5, b = 3.0, c = 4.0, $\alpha=90^\circ, \beta=120^\circ, \gamma=90^\circ$. The crystal system of the substance is :

Match List - I with List - II. 

The major product of the following reaction is :
CH$_3$CH$_2$CH=CH$_2$ + H$_2$/CO $\xrightarrow{\text{Rh catalyst}}$

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 number of stereoisomers possible for 1,2-dimethyl cyclopropane is :
Deuterium resembles hydrogen in properties but :

The major product of the following reaction is : 
(Image shows Benzene reacting with 2-nitropropene in presence of H$_2$SO$_4$) 

Which one of the following is formed (mainly) when red phosphorus is heated in a sealed tube at 803 K ?
What is the correct order of the following elements with respect to their density ?

The product formed in the first step of the reaction of $CH_3 - CH_2 - CH(Br) - CH_2 - CH(Br) - CH_3$ with excess $Mg/Et_2O$ is :

A cube of side 'a' has point charges \(+ Q\) located at each of its vertices except at the origin where the charge is \(-Q\). The electric field at the centre of cube is:
A cube of side 'a' has point charges +Q located at each of its vertices except at the origin where the charge is −Q
In the given figure, a mass \(M\) is attached to a horizontal spring which is fixed on one side to a rigid support. The spring constant of the spring is \(k\). The mass oscillates on a frictionless surface with the time period \(T\) and amplitude \(A\). When the mass is in an equilibrium position, as shown in the figure, another mass \(m\) is gently fixed upon it. The new amplitude of oscillation will be : 
a horizontal spring which is fixed on one side to a rigid support

Match List -I with List -II 

List - IList -II
aIsothermaliPressure constant
bIsobariciiTemperature constant
cAdiabaticiiiVolume constant
dIsobaricivHeat content is constant

Choose the correct answer from the options given below