List of top Questions asked in JEE Main

Five persons $P_1, P_2, P_3, P_4$ and $P_5$ recorded object distance ($u$) and image distance ($v$) using same convex lens having power $+5$ D as (25,96), (30,62), (35,37), (45,35) and (50,32) respectively. Identify correct statement.

In the Young's double slit experiment the intensity produced by each one of the individual slits is $I_0$. The distance between two slits is $2\,\text{mm}$. The distance of screen from slits is $10\,\text{m}$. The wavelength of light is $6000\,\text{\AA}$. The intensity of light on the screen in front of one of the slits is ________.

The reading of the ammeter ($A$) in steady state in the following circuit (assuming negligible internal resistance of the ammeter) is ________ A.

When a light of a given wavelength falls on a metallic surface the stopping potential for photoelectrons is $3.2\ \text{V}$. If a second light having wavelength twice of the first light is used, the stopping potential drops to $0.7\ \text{V}$. The wavelength of the first light is ________ m.

A soap bubble of surface tension $0.04\,\text{N/m}$ is blown to a diameter of $7\,\text{cm}$. If $(15000 - x)\,\mu\text{J}$ of work is done in blowing it further to make its diameter $14\,\text{cm}$ $(\pi = 22/7)$, then the value of $x$ is ________.

A uniform solid cylinder of length $L$ and radius $R$ has moment of inertia about its axis equal to $I_1$. A small co-centric cylinder of length $L/2$ and radius $R/3$ carved from it has moment of inertia about its axis equal to $I_2$. The ratio $I_1/I_2$ is ________.

In a meter bridge experiment to determine the value of unknown resistance, first the resistances $2\,\Omega$ and $3\,\Omega$ are connected in the left and right gaps of the bridge and the null point is obtained at a distance $l$ cm from the left end. Now, when an unknown resistance $x\,\Omega$ is connected in parallel to $3\,\Omega$, the null point is shifted by $10\,\text{cm}$ to the right. The value of $x$ is ________ $\Omega$.

A point charge $q = 1\,\mu\text{C}$ is located at a distance $2\,\text{cm}$ from one end of a thin insulating wire of length $10\,\text{cm}$ having a charge $Q = 24\,\mu\text{C}$, distributed uniformly along its length, as shown in the figure. Force between $q$ and wire is ________ N.

In the group analysis of cations, Ba$^{2+}$ & Ca$^{2+}$ are precipitated respectively as

Given below are two statements:
Statement I: The dipole moment of R–CN is greater than R–NC and R–NC can undergo hydrolysis under acidic medium to produce R–COOH.
Statement II: R–CN hydrolyses under acidic medium to produce a compound which on treatment with SOCl$_2$, followed by the addition of NH$_3$ gives another compound (X). This compound (X) on treatment with NaOCl/NaOH gives a product, that on treatment with CHCl$_3$/KOH/$\Delta$ produces R–NC.
In the light of the above statements, choose the correct answer from the options given below.

``X'' is an oxoanion of the lightest element of group 17 (in the periodic table). The metal is in +6 oxidation state in ``X''. The color of the potassium salt of X is

Choose the INCORRECT statement

Two liquids A and B form an ideal solution at temperature T K. At T K, the vapour pressures of pure A and pure B are 55 and 15 kPa respectively. What is the mole fraction of A in solution of A and B in equilibrium with a vapour in which the mole fraction of A is 0.8?

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is

Given below are two statements regarding conformations of n-butane. Choose the correct option.

At 298 K, the mole percentage of N$_2$(g) in air is 80%. Water is in equilibrium with air at a pressure of 10 atm. What is the mole fraction of N$_2$(g) in water at 298 K? ($K_H$ for N$_2$ = $6.5 \times 10^7$ mm Hg)

The wavelength of light absorbed for the following complexes are in the order
[Co(NH$_3$)$_6$]$^{3+}$ (I), [Co(H$_2$O)$_6$]$^{3+}$ (II), [Co(CN)$_6$]$^{3-}$ (III), [Co(NH$_3$)$_5$(H$_2$O)]$^{3+}$ (IV), [CoF$_6$]$^{3-}$ (V)

Consider the following gaseous equilibrium in a closed container of volume $V$ at temperature $T$:
P$_2$(g) + Q$_2$(g) $\rightleftharpoons$ 2PQ(g)
Initially, 2 moles each of P$_2$(g), Q$_2$(g) and PQ(g) are present at equilibrium. One mole each of P$_2$ and Q$_2$ are added. The number of moles of P$_2$, Q$_2$ and PQ at the new equilibrium respectively are

Given below are two statements:
Statement I: Cross aldol condensation between two different aldehydes will always produce four different products.
Statement II: When semicarbazide reacts with a mixture of benzaldehyde and acetophenone under optimum pH, it forms a condensation product with acetophenone only.

The wavelength of spectral line obtained in the spectrum of Li$^{2+}$ ion, when the transition takes place between two levels whose sum is 4 and difference is 2, is

The heat of atomisation of methane and ethane are $ x $ kJ mol$^{-1}$ and $ y $ kJ mol$^{-1}$ respectively. The longest wavelength ($ \lambda $) of light capable of breaking the C–C bond can be expressed in SI unit as:

Find out the statements which are not true.
A. Resonating structures with more covalent bonds and less charge separation are more stable.
B. In electromeric effect, an unsaturated system shows +E effect with nucleophile and –E effect with electrophile.
C. Inductive effect is responsible for high melting point, boiling point and dipole moment of polar compounds.
D. The greater the number of alkyl groups attached to the doubly bonded carbon atoms, higher is the heat of hydrogenation.
E. Stability of carbanion increases with increase in s-character of the carbon carrying negative charge.

The correct order of C, N, O and F in terms of second ionisation potential is

A student has planned to prepare acetanilide from aniline using acetic anhydride. The student has started from 9.3 g of aniline. However, the student has managed to obtain 11 g of dry acetanilide. The % yield of this reaction is

The half-life of $^{65}$Zn is 245 days. After $x$ days, 75% of the original activity remained. The value of $x$ in days is __________ (Nearest integer).}
(Given: $\log 3 = 0.4771$ and $\log 2 = 0.3010$)