Recent questions in JEEMAIN PAST PAPERS

For a first order reaction, $(A) \to products$, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is :

asked Dec 11, 2018 by pady_1

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The electrons identified by quantum numbers n and I : (a) n = 4, I = 1 (b) n = 4, I = 0 (c) n = 3, I = 2 (d) n = 3, I = 1 Can be placced in order of increasing energy as :

asked Dec 11, 2018 by pady_1

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Very pure hydrogen (99.9%) can be made by which of the following processes ?

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How many chiral compounds are possible on monochlorination of 2-methyl butane ?

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Ortho-Nitrophenol is less soluble in water than p- and m- Nitrophenols because :

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Aspirin is known as :

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Which one of the following statements is correct ?

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The compressibility factor for a real gas at high pressure is :

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The equilibrium constant $(K_C)$ for the reaction $N_2(g) + O_2(g) \to 2NO (g)$ at temperature T is $ 4 \times 10^{-4}$. The value of $K_C$ for the reaction, $NO(g) \to 1/2 N_2 (g) + 1/2 O_2 (g)$ at the same temperature is :

asked Dec 11, 2018 by pady_1

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According toFreundiich adsorption isotherm, which of the following is correct ?

asked Dec 11, 2018 by pady_1

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The standard reduction potentials for $Zn^{2+}/Zn, Ni^{2+}/Ni$ and $Fe^{2+}/Fe$ are -0.76, -0.23 and -0.44V respectively. The reaction $X + Y^2 \to X^{2+} + Y$ will be spontaneous when :

asked Dec 11, 2018 by pady_1

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Which of the following on thermal decomposition yields a basic as well as an acidic oxide ?

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The species which can best serve as an initiator for the cationic polymerization is :

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The density of a solution prepared by dissolving 120 g of urea ( mol. Mass = 60 u) in 1000 g of water is 1.15 g/mL. The molarity of this solution is :

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The incorrect expression among the following is :

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Which of the following compounds can be detected by Molisch's test ?

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The molecule having smallest bond angle is :

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Lithium forms body centred cubic structure. The length of the side of its unit cell is 351 pm. Atomic radius of the lithium will be :

asked Dec 11, 2018 by pady_1

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Which method of purification is represented by the following equation : $Ti(s) + 2I_2 (g) \xrightarrow{523 K} TiI_4 (g) \xrightarrow{1700 K} Ti(s) + 2I_2 (g)$

asked Dec 11, 2018 by pady_1

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Which among he following will be named as dibromidobis (ethylene diamine) chrominum (III) bromide ?

asked Dec 11, 2018 by pady_1

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Proton, Deuteron and alpha particle of the same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, deuteron and alpha particle are respecctively $r_p$, $r_d$ and $r_{\alpha}$. Which one of the following relations is correct ?

asked Dec 11, 2018 by pady_1

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This question has statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements. An insulating solid sphere of radius R has a uniformly positive charge density $\rho$. As a result of this uniform charge distribution there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere and also at a point out side the sphere. The electric potential at infinity is zero. Statement 1 : When a charge q is taken from the centre to the surface of the sphere, its potential energy changes by $\frac{qp}{3 \varepsilon_0}$ Statement 2 : The electric field at a distance r (r < R) from the centre of the sphere is $\frac{\rho r}{ 3 \varepsilon_0}$

asked Dec 11, 2018 by pady_1

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A spectrometer gives the following reading when used to measure the angle of a prism. Main scale reading : 58.5 degree Vernier scale reading : 09 divisions Given that 1 division on main scale corresponds to 0.5 degree. Total divisions on the vernier scale is 30 and match with 29 divisions of the main scale. The angle of the prism from the above data

asked Dec 11, 2018 by pady_1

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A diatomic molecule is made of two masses $m_1$ and $m_2$ which are separated by a distance $r$. If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by (n is an integer)

asked Dec 11, 2018 by pady_1

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An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1 cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object be shifted to be in sharp focus on film ?

asked Dec 11, 2018 by pady_1

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A cylindrical tube, open at both ends, has a fundamental frequency, f, in air. The tube is dipped vertically in water so that half of it is in water. The fundamental frequency of the air-column is now

asked Dec 11, 2018 by pady_1

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Two cars of masses $m_1$ and $m_2$ are moving in circles of radii $r_1$ and $r_2$, respectively. Their speeds are such that they make complete circles in the same times t. The ratio of their centripetal acceleration is

asked Dec 11, 2018 by pady_1

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This question has statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements If two springs $S_1$ and $S_2$ of force constants $k_1$ and $k_2$, respectively, are stretched by the same force, it is found that more work is done on spring $S_1$ than on spring $S_2$. If stretched by the same amount, work done on $S_1$, will be more than that on $S_2$. Statement 2 : $k_1 < k_2$.

asked Dec 11, 2018 by pady_1

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A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500 K. It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) temperature must be

asked Dec 11, 2018 by pady_1

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Assume that a neutron breaks into a proton and an electron. The energy released during this process is (Mass of neutron = $1.6725 \times 10^{-27}\;kg$; mass of proton = $1.6725 \times 10^{-27} \;kg$ mass of electron = $9 \times 10^{-31}\; kg $)

asked Dec 11, 2018 by pady_1

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A radar has a power of 1 Kw and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth = $6.4 \times 10^{6} m$ ) is

asked Dec 11, 2018 by pady_1

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Truth table for system of four NAND gates as shown in figure is

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A charge Q is uniformly distributed over the surface of non conducting disc of radius R. The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity $\omega$. As a result of this rotation a magnetic field of induction B is obtained at the centre of the disc. If we keep both the amount of charge placed on the disc and its angular velocity of be constant and vary the radius of the disc then the variation of the magnetic induction at the centre of the disc will be represented by the figure

asked Dec 11, 2018 by pady_1

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A thin liquid film formed between a U-shaped wire and a light slider supports a weight of $1.5 \times 10^{-2}N$ (see figure). The length of the slider is 30 cm and its weight negligible. The surface tension of the liquid film is

asked Dec 11, 2018 by pady_1

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This question has statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements Statement 1 : Davisson-germer experiment established the wave nature of electrons. Statement 2 : If electrons have wave nature, they can interfere and show diffraction.

asked Dec 11, 2018 by pady_1

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A boy can throw a stone up to a maximum height of 10 m. The maximum horizontal distance that the boy can throw the same stone up to will be

asked Dec 11, 2018 by pady_1

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Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are 3% each, then error in the value of resistance of the wire is

asked Dec 11, 2018 by pady_1

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Two electric bulbs marked 25 W - 220 V and 100 W - 220 V are connected in series to a 440 V supply. Which of the bulbs will fuse ?

asked Dec 11, 2018 by pady_1

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A particle of mass m is at rest at the origin at time t=0. It is subjected to a force $F(t) = F_0e^{-bt}$ in the $x$ direction. Its speed v(t) is depicted by which of the following curves ?

asked Dec 11, 2018 by pady_1

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A liquid in a beaker has temperature $\theta(t)$ at time $t$ and $\theta_0$ is temperature of surroundings, then according to Newton's law of cooling the correct graph between $log_e (\theta - \theta_0)$ and $t$ is

asked Dec 11, 2018 by pady_1

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In Young's double slit experiment, one of the slit is wider than other, so that the amplitude of the light from one slit is double of that from other slit. If $I_m$ be the maximum intensity, the resultant intensity $I$ when they interfere at phase difference $\phi$ is given by

asked Dec 11, 2018 by pady_1

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Helium gas goes through a cycle ABCDA (consisting of two isochoric and two isobaric lines) as shown in figure. Efficiency of this cycle is nearly : (Assume the gas to be close to ideal gas )

asked Dec 11, 2018 by pady_1

1 answer

The mass of a spaceship is 1000 kg. It is to be launched from the earth's surface out into free space. The value of 'g' and 'R' (radius of earth) are $10\; m/s^2$ and 6400 km respectively. The required energy for this work will be :

asked Dec 11, 2018 by pady_1

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A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating; it is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to :

asked Dec 11, 2018 by pady_1

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Hydrogen atom is excited from ground state to another state with pricipal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be

asked Dec 11, 2018 by pady_1

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If a simple pendulum has significant amplitude (up to a factor of 1/e of original) only in the period between $t = Os$ to $ t = \tau s$, then $\tau$ may be called the average life of the pendulum. When the spherical bob of the pendulum suffers a retardation (due to viscous drag) proportional to its velocity, with 'b' as the constant of proportionality, the average life time of the pendulum is ( assuming damping is small ) in seconds :

asked Dec 11, 2018 by pady_1

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An electromagnetic wave in vacuum has the electric and magnetic fields $\overrightarrow{E}$ and $\overrightarrow{B}$, which are always perpendicular to each other. The direction of polarization is given by $\overrightarrow{X}$ and that of wave propagation by $\overrightarrow{k}$. Then :

asked Dec 11, 2018 by pady_1

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In a uniformly charged sphere of total charge Q and radius R, the electric field E is plotted as a function of distance from the centre. The graph which would correspond to the above will be

asked Dec 11, 2018 by pady_1

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The figure shows an experimental plot for discharging of a capacitor in an R-C circuit. The time constant $\tau$ of this circuit lies between :

asked Dec 11, 2018 by pady_1

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A wooden wheel of radius $R$ is made of two semicircular parts (see figure); The two parts are held together by a ring made of a metal strip of cross sectional area $S$ and length $L$. $L$ is slightly less than $2 \pi R$. To fit the ring on the wheel, it is heated so that its temperature rises by $\Delta T$ and it just steps over the wheel. As it cools down to surrounding temperature, it presses the semicircular parts together. If the coefficient of linear expansion of the metal is $\alpha$, and its Youngs' modulus is $Y$, the force that one part of the wheel applies on the other part is :

asked Dec 11, 2018 by pady_1

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