Recent questions in JEEMAIN PAST PAPERS

What volume of hydrogen gas, at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by hydrogen ?

asked Dec 11, 2018 by pady_1

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Consider the reaction equilibrium : $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3 (g); \; \; \; \Delta H^{\circ} = -198 kJ$ On the basis of Le-Chatelier's principle, the condition favourable for the forward reaction is :

asked Dec 11, 2018 by pady_1

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The atomic numbers of vanadium (V), chromium (Cr), manganese (Mn) and iron (Fe) are respectively 23, 24, 25 and 26. Which one of these may be expected to have the highest second ionization enthalpy ?

asked Dec 11, 2018 by pady_1

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The pair of species having identical shapes for molecules of both species is :

asked Dec 11, 2018 by pady_1

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In the anion $HCOO^-$ the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?

asked Dec 11, 2018 by pady_1

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Which one of the following groupings represents a collection of isoelectronic species ? (At. numbers : Cs - 55, Br - 35)

asked Dec 11, 2018 by pady_1

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Which one of the following pairs of molecules will have permanent dipole moments for both members ?

asked Dec 11, 2018 by pady_1

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Which one of the following compounds has the smallest bond angle in its molecule ?

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Which one of the following processes will produce hard water ?

asked Dec 11, 2018 by pady_1

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Among the following four structures $I$ to $IV$ : it is true that :

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An ether is more volatile than an alcohol having the same molecular formula. This is due to :

asked Dec 11, 2018 by pady_1

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The general formula $C_n H_{2n} O_2$ could be for open chain :

asked Dec 11, 2018 by pady_1

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Which of the following group of transition metals is called coinage metals ?

asked Dec 11, 2018 by pady_1

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According to the kinetic theory of gases, in an ideal gas, between two successive collisions a gas molecule travels :

asked Dec 11, 2018 by pady_1

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When $CH_2 = CH - COOH$ is reduced with $LiAlH_4$, the compound obtained will be :

asked Dec 11, 2018 by pady_1

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The IUPAC name of $CH_3COCH(CH_3)_2$ is :

asked Dec 11, 2018 by pady_1

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Graphite is a soft solid lubricant extremely difficult to melt. The reason for this anomalous behaviour is that graphite :

asked Dec 11, 2018 by pady_1

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According to the periodic law of elements, the variation in properties of elements is related to their :

asked Dec 11, 2018 by pady_1

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Which one of the following statements is correct ?

asked Dec 11, 2018 by pady_1

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Glass is a :

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How many unit cells are present in a cube shaped ideal crystal of $NaCl$ of mass $1.00\;g$ ? [Atomic masses : Na = 23, Cl = 35.5]

asked Dec 11, 2018 by pady_1

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The orbital angular momentum for an electron revolving in an orbit is given by $\sqrt{l(l+1)} \frac{h}{2 \pi} $. The momentum for an s-electron will be given by :

asked Dec 11, 2018 by pady_1

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The de-Broglie wavelength of a tennis ball of mass 60 g moving with a velocity of 10 m/s is approximately : (Plancks constant, $h =6.63 \times 10^{-34} Js$)

asked Dec 11, 2018 by pady_1

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In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inner-orbit jumps of the electron for Bohr orbits in an atom of hydrogen ?

asked Dec 11, 2018 by pady_1

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The length of a given cylindrical wire is increased by 100%. Due to the consequent decrease in diameter the change in the resistance of the wire will be :

asked Dec 11, 2018 by pady_1

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According to Newton's law of cooling, the rate of cooling of a body is proportional to $(\Delta \theta)^n$, where $\Delta \theta$ is the difference of the temperature of the body and the surroundings, and $n$ is equal to :

asked Dec 11, 2018 by pady_1

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To get three images of a single object, one should have two plane mirrors at an angle of :

asked Dec 11, 2018 by pady_1

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The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by :

asked Dec 11, 2018 by pady_1

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The image formed by an objective of a compound microscope is :

asked Dec 11, 2018 by pady_1

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A 220 V, 1000 W bulb is connected across a 110 V mains supply. The power conumed will be :

asked Dec 11, 2018 by pady_1

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Three charges $-q_1,\;+q_2$ and $-q_3$ are placed as shown in the figure. The x-component of the force on $-q_1$ is proportional to :

asked Dec 11, 2018 by pady_1

1 answer

To demonstrate the phenomenon of interference we require two sourcces which emit radiations of :

asked Dec 11, 2018 by pady_1

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A rocket with a lift-off mass $3.5 \times 10^4 kg$ is blasted upwards with an initial acceleration of $10 m/s^2$. Then the initial thrust of the blast is :

asked Dec 11, 2018 by pady_1

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A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time t is proportional to :

asked Dec 11, 2018 by pady_1

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If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of $Li^{2+}$ is

asked Dec 11, 2018 by pady_1

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In the middle of the depletion layer of reverse biased p-n junction, the :

asked Dec 11, 2018 by pady_1

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The wavelengths involved in the spectrum of deuterium $(_1^2D)$ are slightly different from that of hydrogen spectrum, because :

asked Dec 11, 2018 by pady_1

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Which of the following atoms has the lowest ionization potential ?

asked Dec 11, 2018 by pady_1

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In the nuclear fusion reaction, $_1^2H +_1^3H \to _2^4He+n$ given that the repulsive potential energy between the two nuclei is $7.7 \times 10^{-14} J$, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann's constant $k = 1.38 \times 10^{-23} J/K$] :

asked Dec 11, 2018 by pady_1

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A body executes simple harmonic motion.The potential energy (PE), the kinetic energy (KE) and total energy (TE) are measured as function of displacement $x$. Which of the following statement is true ?

asked Dec 11, 2018 by pady_1

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A tuning fork of known frequency 256 Hz makes 5 beats/s with the vibrating string of a piano. The beat frequency decreases to 2 beats/s when the tension in the piano string is slightly increased. The frequency of the piano string before increaseing the tension was :

asked Dec 11, 2018 by pady_1

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A metal wire of linear mass density of 9.8 g/m is streched with a tension of 10 kg-wt between two rigid supports 1 m apart. The wire passes at its middle point between the poles of a permanent magnet and it vibrates in resonance when carrying an alternating current of frequency n. The frequency n of the alternating source is :

asked Dec 11, 2018 by pady_1

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A spring of spring constant $5 \times 10^3 N/m$ is stretched initially by 5 cm from the unstreched position. Then the work required to stretch it further by another 5 cm is

asked Dec 11, 2018 by pady_1

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A Carnot engine takes $3 \times 10^6$ cal of heat from a reservoir at $627^{\circ}C$ and gives it to a sink at $27^{\circ}C$. The work done by the engine is :

asked Dec 11, 2018 by pady_1

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Which of the following parameters does not characterise the thermodynatic state of matter ?

asked Dec 11, 2018 by pady_1

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During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio $C_P/C_V$ for the gas is :

asked Dec 11, 2018 by pady_1

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The co-ordinates of a moving particle at any time $t$ are given by $x = \alpha t^3$ and $y = \beta t^3$. The speed of the particle at time $t$ is given by :

asked Dec 11, 2018 by pady_1

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The work done in placing a charge of $8 \times 10^{-18} C$ on a condenser of capacity $100 \mu F$ is :

asked Dec 11, 2018 by pady_1

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A thin spherical conducting shell of radius $R$ has a charge $q$. Another charge $Q$ is placed at the centre of the shell. The electrostatic potential at a point $P$ at a distance $R/2$ from the centre of the shell is :

asked Dec 11, 2018 by pady_1

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The displacement of a particle varies according to the relation $x=4 (\cos \pi t + \sin \pi t)$. The amplitude of the particle is :

asked Dec 11, 2018 by pady_1

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