List of top Questions asked in JEE Main- 2021

The correct statements about \(\mathrm{H_2O_2}\) are :

(A) used in the treatment of effluents.

(B) used as both oxidising and reducing agents.

(C) the two hydroxyl groups lie in the same plane.

(D) miscible with water.

Choose the correct answer from the options given below :

The green house gas/es is (are) :

(A) Carbon dioxide

(B) Oxygen

(C) Water vapour

(D) Methane

Choose the most appropriate answer from the options given below :

Which of the following reduction reaction CANNOT be carried out with coke?

The INCORRECT statement regarding the structure of \(\mathrm{C_{60}}\) is :

Which of the following polymer is used in the manufacture of wood laminates?

Identify the reagent(s) 'A' and condition(s) for the reaction

Identify the elements X and Y using the ionisation energy values given below :

	1st ionization energy (kJ/mol)	2nd ionization energy (kJ/mol)
X	495	4563
Y	731	1450

In the above reaction, the reagent "A" is :

Arrange the following metal complex/compounds in the increasing order of spin only magnetic moment. Presume all the three, high spin system.

(Atomic numbers Ce = 58, Gd = 64 and Eu = 63)

(a) \(\mathrm{(NH_4)_2[Ce(NO_3)_6]}\)

(b) \(\mathrm{Gd(NO_3)_3}\) and

(c) \(\mathrm{Eu(NO_3)_3}\)

Statement I : Sodium hydride can be used as an oxidising agent.

Statement II : The lone pair of electrons on nitrogen in pyridine makes it basic.

Choose the CORRECT answer from the options given below :

\(\mathrm{FeX_2}\) and \(\mathrm{FeY_3}\) are known when x and y are :

The characteristics of elements X, Y and Z with atomic numbers, respectively, 33, 53 and 83 are :

The secondary structure of protein is stabilised by:

The exact volumes of 1 M NaOH solution required to neutralise 50 mL of 1 M \(\mathrm{H_3PO_3}\) solution and 100 mL of 2 M \(\mathrm{H_3PO_2}\) solution, respectively, are :

Which of the following is least basic?

Ammonolysis of Alkyl halides followed by the treatment with NaOH solution can be used to prepare primary, secondary and tertiary amines. The purpose of NaOH in the reaction is :

A deviation of \(2^\circ\) is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass as 0.02 and 0.03 respectively and refractive index for yellow light for these glasses are 1.5 and 1.6 respectively. The refracting angles for crown glass prism will be ____________\(^\circ\) (in degree). (Round off to the Nearest Integer)

The structure of X is :

An unsaturated hydrocarbon X on ozonolysis gives A. Compound A when warmed with ammonical silver nitrate forms a bright silver mirror along the sides of the test tube. The unsaturated hydrocarbon X is :

For an ideal heat engine, the temperature of the source is \(127^\circ\)C. In order to have 60% efficiency the temperature of the sink should be ___________\(^\circ\)C. (Round off to the Nearest Integer)

Match List - I with List - II :

	List - I Test/Reagents/Observation(s)		List - II Species detected
(a)	Lassaigne's Test	(i)	Carbon
(b)	Cu(II) oxide	(ii)	Sulphur
(c)	Silver nitrate	(iii)	N, S, P, and halogen
(d)	The sodium fusion extract gives black precipitate with acetic acid and lead acetate	(iv)	Halogen Specifically

The correct match is :

A swimmer can swim with velocity of 12 km/h in still water. Water flowing in a river has velocity 6 km/h. The direction with respect to the direction of flow of river water he should swim in order to reach the point on the other bank just opposite to his starting point is ____________\(^\circ\). (Round off to the Nearest Integer) (Find the angle in degrees)

The energy dissipated by a resistor is 10 mJ in 1 s when an electric current of 2 mA flows through it. The resistance is ___________ \(\Omega\). (Round off to the Nearest Integer)

A closed organ pipe of length L and an open organ pipe contain gases of densities \(\rho_1\) and \(\rho_2\) respectively. The compressibility of gases are equal in both the pipes. Both the pipes are vibrating in their first overtone with same frequency. The length of the open pipe is \(\frac{x}{3}L\sqrt{\frac{\rho_1}{\rho_2}}\) where x is ___________. (Round off to the Nearest Integer)

Amplitude of a mass-spring system, which is executing simple harmonic motion decreases with time. If mass = 500 g, Decay constant = 20 g/s then how much time is required for the amplitude of the system to drop to drop to half of its initial value? (ln 2 = 0.693)