List of top Questions asked in JEE Main- 2021

At very high frequencies, the effective impedance of the given circuit will be ________ \(\Omega\). 

A long solenoid with 1000 turns/m has a core material with relative permeability 500 and volume \(10^3\) cm\(^3\). If the core material is replaced by another material having relative permeability of 750 with same volume maintaining same current of 0.75 A in the solenoid, the fractional change in the magnetic moment of the core would be approximately \(\left( \frac{x}{499} \right)\). Find the value of x.
A resistor dissipates 192 J of energy in 1 s when a current of 4 A is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in 5 s is _________ J.
The incorrect expression among the following is :
Which one of the following statements is incorrect?
In which one of the following sets all species show disproportionation reaction ?
The deposition of X and Y on ground surfaces is referred as wet and dry depositions, respectively. X and Y are :

Arrange the following conformational isomers of n-butane in order of their increasing potential energy : 
 

For the following sequence of reactions, the correct products are : 

For the reaction given below : 
The compound which is not formed as a product in the reaction is a : 
 

The structures of A and B formed in the following reaction are : [Ph = \(-C_6H_5\)] 

Identify correct A, B and C in the reaction sequence given below : 
 

Which among the following is not a polyester ?
Which of the following is NOT an example of fibrous protein ?

Match List - I with List - II :

List - I (Metal Ion)List - II (Group in Qualitative analysis)
(a) \( \text{Mn}^{2+} \)(i) Group - III
(b) \( \text{As}^{3+} \)(ii) Group - IIA
(c) \( \text{Cu}^{2+} \)(iii) Group - IV
(d) \( \text{Al}^{3+} \)(iv) Group - IIB

Choose the most appropriate answer from the options given below :

Sodium oxide reacts with water to produce sodium hydroxide. 20.0 g of sodium oxide is dissolved in 500 mL of water. Neglecting the change in volume, the concentration of the resulting NaOH solution is ________ $\times 10^{-1}$ M. (Nearest integer) [Atomic mass : Na = 23.0, O = 16.0, H = 1.0]
The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites is $A_x B$. The value of $x$ is ________. (Integer answer)
The value of magnetic quantum number of the outermost electron of $\text{Zn}^+$ ion is ________. (Integer answer)
According to molecular orbital theory, the number of unpaired electron(s) in $\text{O}_2^{2-}$ is ________.
1.22 g of an organic acid is separately dissolved in 100 g of benzene ($K_b = 2.6 \text{ K kg mol}^{-1}$) and 100 g of acetone ($K_b = 1.7 \text{ K kg mol}^{-1}$). The acid is known to dimerize in benzene but remain as a monomer in acetone. The boiling point of the solution in acetone increases by $0.17^\circ\text{C}$. The increase in boiling point of solution in benzene in $^\circ\text{C}$ is $x \times 10^{-2}$. The value of $x$ is ________. (Nearest integer) [Atomic mass : C = 12.0, H = 1.0, O = 16.0]
The pH of a solution obtained by mixing 50 mL of 1 M HCl and 30 mL of 1 M NaOH is $x \times 10^{-1}$. The value of $x$ is ________. (Nearest integer) [log 2.5 = 0.3979]
For the reaction $\text{A} \to \text{B}$, the rate constant $k$ (in $\text{s}^{-1}$) is given by $\log_{10} k = 20.35 - \frac{2.47 \times 10^3}{\text{T}}$. The energy of activation in $\text{kJ mol}^{-1}$ is ________. (Nearest integer) [Given : R = 8.314 J K$^{-1}$ mol$^{-1}$]
$\text{CH}_4$ is adsorbed on 1 g charcoal at $0^\circ\text{C}$ following the Freundlich adsorption isotherm. 10.0 mL of $\text{CH}_4$ is adsorbed at 100 mm of Hg, whereas 15.0 mL is adsorbed at 200 mm of Hg. The volume of $\text{CH}_4$ adsorbed at 300 mm of Hg is $10^x$ mL. The value of $x$ is ________ $\times 10^{-2}$. (Nearest integer) [Use $\log_{10} 2 = 0.3010, \log_{10} 3 = 0.4771$]
In the electrolytic refining of blister copper, the total number of main impurities, from the following, removed as anode mud is ________.
Pb, Sb, Se, Te, Ru, Ag, Au and Pt.
The transformation occurring in Duma's method is given below:
$\text{C}_2 \text{H}_7 \text{N} + (2x + y/2) \text{CuO} \to x \text{CO}_2 + y/2 \text{H}_2\text{O} + z/2 \text{N}_2 + (2x + y/2) \text{Cu}$.
The value of $y$ is ________. (Integer answer)