List of top Questions asked in JEE Main

$50\, mL$ of $0.5\, M$ oxalic acid is needed to neutralize $25\, mL$ of sodium hydroxide solution. The amount of $NaOH$ in $50\, mL$ of the given sodium hydroxide solution is :

For a reaction, $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$; identify dihydrogen $(H_2)$ as a limiting reagent in the following reaction mixtures.

During compression of a spring the work done is $10\,kJ$ and $2\,kJ$ escaped to the surroundings as heat. The change in internal energy, $\Delta\, U(in\,kJ)$ is:

Enthalpy of sublimation of iodine is $ {24 \; cal \; g^{-1}}$ at $200^{\circ}C$. If specific heat of $I_2(s)$ and $I_2(vap)$ are $0.055$ and $0.031\, cal\, g^{-1}K^{-1}$ respectively, then enthalpy of sublimation of iodine at $250^{\circ}C$ in $cal\, g^{-1}$ is :

For diatomic ideal gas in a closed system, which of the following plots does not correctly describe the relation between various thermodynamic quantities ?

For silver, $ {C_{p}(JK^{-1} mol^{-1}) = 23 + 0.01T}$. If the temperature (T) of $3$ moles of silver is raised from $300\,K$ to $1000\, K$ at $1\, atm$ pressure, the value of $\Delta H$ will be close to

Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas ? (Assume non-expansion work is zero)

$5$ moles of an ideal gas at $100\, K$ are allowed to undergo reversible compression till its temperature becomes $200\, K$. If $C_{V} =28 JK^{-1}mol^{-1} , caculate \Delta\, U$ and $\Delta \,pV $ for this process. ($R = 8.0 \, JK^{-1}mol^{-1}$]

Which one of the following statements regarding Henry's law not correct ?

For emission line of atomic hydrogen from $n_i = 8$ to $n_f $ = the plot of wave number $(\bar{v})$ against $( \frac{1}{n^2})$ will be (The Ry dberg constant, $R_H$ is in wave number unit).

Heat treatment of muscular pain involves radiation of wavelength of about $900\, nm$. Which spectral line of H-atom is suitable for this purpose ? $[R_H = 1 \times 10^5 \; cm^{-1}, h = 6.6 \times 10^{-34} \; Js, c = 3 \times 10^8 \; ms^{-1}]$

The size of the iso-electronic species $Cl^-, Ar$ and $ {Ca^{2+}}$ is affected by -

If surface tension (S), Moment of inertia (I) and Planck's constant (h), were to be taken as the fundamental units, the dimensional formula for linear momentum would be : -

A person standing on an open ground hears the sound of a jet aeroplane, coming from north at an angle $60^\circ$ with ground level. But he finds the aeroplane right vertically above his position. If $\upsilon$ is the speed of sound, speed of the plane is :

In a car race on straight road, car $A$ takes a time $t$ less than car $B$ at the finish and passes finishing point with a speed $'v'$ more than that of car $B$. Both the cars start from rest and travel with constant acceleration $a_1$ and $a_2$ respectively. Then $'v'$ is equal to :

In the cube of side $'a'$ shown in the figure, the vector from the central point of the face $ABOD$ to the central point of the face $BEFO$ will be:

Two vectors $\vec{A}$ and $\vec{B}$ have equal magnitudes. The magnitude of $(\vec{A} + \vec{B})$ is 'n' times the magnitude of $(\vec{A} - \vec{B})$ . The angle between $\vec{A}$ and $\vec{B}$ is :

Condiser the nuclear fission ${Ne^{20} -> 2 He^{4} + C^{12}} $ Given that the binding energy/nucleon of ${Ne^{20}, He^{4}}$ and ${C^{12}}$ are, respectively, 8.03 MeV, 7.07 MeV and 7.86 MeV, identify the correct statement :

Two radioactive materials $A$ and $B$ have decay constants $10 \lambda$ and $\lambda$, respectively. It initially they have the same number of nuclei, then the ratio of the number of nuclei of $A$ to that of $B$ will be $1/e$ after a time :

The ratio of mass densities of nuclei of $^{40}C_a$ and $^{16}O$ is close to :-

A sample of radioactive material $A$, that has an activity of $10 \; mCi (1 \; Ci = 3.7 \times 10^{10}$ decays/s), has twice the number of nuclei as another sample of a different radioactive maternal $B$ which has an activity of $20\, mCi$. The correct choices for hall-lives of $A$ and $B$ would then be respectively :

Consider an electron in a hydrogen atom, revolving in its second excited state (having radius $4.65\,?$). The de-Broglie wavelength of this electron is :

In a hydrogen like atom, when an electron jumps from the $M$ - shell to the $L$ - shell, the wavelength of emitted radiation is $\lambda$. If an electron jumps from $N$-shell to the $L$-shell, the wavelength of emitted radiation will be :

In $Li^{++}$, electron in first Bohr orbit is excited to a level by a radiation of wavelength $\lambda$. when the ion gets deexcited to the ground state in all possible ways (including intermediate emissions), a total of six spectral lines are observed. What is the value of $\lambda$ ? (Given : $h = 6.63 \times 10^{-34} \; Js ; c = 3 \times 10^8 \; ms^{-1})$ ;

A plano-convex lens (focal length $f_2$, refractive index $\mu_2$, radius of curvature $R$) fits exactly into a plano-concave lens (focal length $f_1$, refractive index $\mu_2$, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :