Recent questions in JEEMAIN PAST PAPERS

If two glass plates have water between them and are separated by very small distance (see figure), it is very difficult to pull them apart. It is because the water in between forms cylindrical surface on the side that gives rise to lower pressure in the water in comparison to atmosphere. If the radius of the cylindrical surface is R and surface tension of water is T then the pressure in water between the plates is lower by :

asked Dec 11, 2018 by pady_1

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If it takes 5 minutes to fill a 15 litre bucket from a water tap of diameter $\frac{2}{\sqrt{\pi}}$ then the Reynolds number for the flow is (density of water $=10^3\; kg/m^3$ and viscosity of water $=10^{-3}$ Pa.s) close to :

asked Dec 11, 2018 by pady_1

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A very long (length L) cylindrical galaxy is made of uniformly distributed mass and has radius $R(R << L)$. A star outside the galaxy is orbiting the galaxy in a plane perpendicular to the galaxy and passing through its centre. If the time period of star is T, and its distance from the galaxy's axis is $r$, then :

asked Dec 11, 2018 by pady_1

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Consider a thin uniform square sheet made of a rigid material. If its side is $'a'$, mass m and moment of inertia I about one of its diagonals, then :

asked Dec 11, 2018 by pady_1

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A uniform solid cylindrical roller of mass $'m'$ is being pulled on a horizontal surface with force $F$ parallel to the surface and applied at its centre. If the acceleration of the cylinder is $'a'$ and it is rolling without slipping then the value of $'F$ is :

asked Dec 11, 2018 by pady_1

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A block of mass $m=0.1 \;kg$ is connected to a spring of unknown spring constant $k$. It is compressed to a distance $x$ from its equilibrium position and released from rest. After approaching half the distance$(\frac{x}{2})$ from equilibrium position, it hits another block and comes to rest momentarily, while the other block moves with a velocity $3 \;ms^{-1}$ . The total initial energy of the spring is :

asked Dec 11, 2018 by pady_1

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A block of mass $m =10\; kg$ rests on a horizontal table. The coefficient of friction between the block and the table is $0.05$. When hit by a bullet of mass $50\; g$ moving with speed $v$, that gets embedded in it, the block moves and comes to stop after moving a distance of $2\; m$ on the table. If a freely falling object were to acquire speed $\frac{v}{10}$ after being dropped from height $H$, then neglecting energy losses and taking $g=10\; ms^{-2}$ , the value of $H$ is close to :

asked Dec 11, 2018 by pady_1

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If a body moving in a circular path maintains constant speed of $10\; ms^{-1}$ , then which of the following correctly describes relation between acceleration and radius ?

asked Dec 11, 2018 by pady_1

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$x$ and $y$ displacements of a particle are given as $x(t) = a \sin \omega t$ and $y(t) = a \sin 2 \omega t$. Its trajectory will look like :

asked Dec 11, 2018 by pady_1

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The most suitable reagent for the conversion of $R-CH_2- OH \to R - CHO$ is:

asked Dec 11, 2018 by pady_1

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For complete combustion of ethanol, $C_2H_5OH (\ell) + 3O_2 (g) \to 2CO_2 (g) + 3H_2O (\ell)$, the amount of heat produced as measured in bomb calorimeter, is $1364.47\; kJ \;mol^{–1}$ at $25^{\circ}C$. Assuming ideality the Enthalpy of combustion, $\Delta_CH$, for the reaction will be: $(R = 8.314\; kJ \;mol^{–1} )$

asked Dec 11, 2018 by pady_1

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Among the following oxoacids, the correct decreasing order of acid strength is:

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Which one is classified as a condensation polymer?

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The ratio of masses of oxygen and nitrogen in a particular gaseous mixture is 1 : 4. The ratio of number of their molecule is:

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Given below are the half-cell reactions : $Mn^{2+} + 2e^- \to Mn; \; E^0 = -1.18 \;V$ $2(Mn^{3+} + e^- \to Mn^{2+} ) \; ; E^0 = +1.51 \; V$ The $E^0$ for $2Mn^{2+} \to Mn + 2Mn^{3+} $ will be :

asked Dec 11, 2018 by pady_1

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The major organic compound formed by the reaction of 1, 1, 1-trichloroethane with silver powder is :

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The correct set of four quantum numbers for the valence elections of rubidium atom (Z= 37) is:

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Which one of the following bases is not present in DNA?

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Considering the basic strength of amines in aqueous solution, which one has the smallest $pK_b$ value?

asked Dec 11, 2018 by pady_1

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Which series of reactions correctly represents chemical reactions related to iron and its compound?

asked Dec 11, 2018 by pady_1

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For the non â€“ stoichiometre reaction $2A +B \to C + D$ , the following kinetic data were obtained in three separate experiments, all at $298\; K$. The rate law for the formation of C is:

asked Dec 11, 2018 by pady_1

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For which of the following molecule significant $\mu \neq 0$?

asked Dec 11, 2018 by pady_1

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The equation which is balanced and represents the correct product(s) is:

asked Dec 11, 2018 by pady_1

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The correct statement for the molecule, $CsI_3$ is:

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On heating an aliphatic primary amine with chloroform and ethanolic potassium hydroxide, the organic compound formed is:

asked Dec 11, 2018 by pady_1

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Sodium phenoxide when heated with $CO_2$ under pressure at $125^{\circ}C$ yields a product which on acetylation produces $C$. The major product C would be:

asked Dec 11, 2018 by pady_1

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In the reaction, $CH_3COOH \xrightarrow{LiAlH_4} A \xrightarrow{PCl_5} B \xrightarrow{Alc. KOH} C$, the product C is :

asked Dec 11, 2018 by pady_1

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For the reaction, $SO_{2(g)} + \frac{1}{2}O_{2(g)} \leftrightharpoons SO_{3(g)}$, if $K_P = K_C(RT)^x$ where the symbols have usual meaning then the value of $x$ is: (assuming ideality)

asked Dec 11, 2018 by pady_1

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The equivalent conductance of NaCl at concentration C and at infinite dilution are $\lambda_C$ and $\lambda_{\infty}$, respectively. The correct relationship between $\lambda_C$ and $\lambda_{\infty}$ is given as: (where the constant B is positive)

asked Dec 11, 2018 by pady_1

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For the estimation of nitrogen, $1.4\; g$ of organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in $60 \;mL$ of $\frac{M}{10}$ sulphuric acid. The unreacted acid require$20\; ml$ of $\frac{M}{10}$ sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is:

asked Dec 11, 2018 by pady_1

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The octahedral complex of a metal ion $M^{3+}$ with four monodentate ligands $L_1, L_2, L_3$ and $L_4$ absorb wavelengths in the region of red, green, yellow and blue, respectively. The increasing order of ligand strength of the four ligands is:

asked Dec 11, 2018 by pady_1

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In $S_N2$ reactions, the correct order of reactivity for the following compounds: $CH_3Cl, \;CH_3CH_2Cl,\; (CH_3)_2CHCl$ and $(CH_3)_3CCl$ is:

asked Dec 11, 2018 by pady_1

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In which of the following reactions $H_2O_2$ acts as a reducing agent? (a) $H_2O_2 +2H^+ + 2e^- \to 2H_2O$ (b) $H_2O_2 - 2e^- \to O_2 + 2H^+$ (c) $H_2O_2 + 2e^- \to 2OH^- $ (d) $H_2O_2 + 2OH^- - 2e^- \to O_2 + 2H_2O$

asked Dec 11, 2018 by pady_1

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Consider separate solutions of $0.500\; M\; C_2H_5OH(aq),\; 0.100\; M \;Mg_3(PO_4)_2(aq),\; 0.250\; M\; KBr(aq)$ and $0.125 \;M \;Na_3PO_4(aq)$ at $25^{\circ}C$. Which statement is true about these solutions, assuming all salts to be strong electrolytes?

asked Dec 11, 2018 by pady_1

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CsCl crystallises in body centred cubic lattice. If ‘a’ is its edge length then which of the following expressions is correct?

asked Dec 11, 2018 by pady_1

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Resistance of $0.2\; M$ solution of an electrolyte is $50 \Omega$. The specific conductance of the solution is $1.4 \;S m^{-1}$ . The resistance of $0.5\; M$ solution of the same electrolyte is $280 \Omega$. The molar conductivity of $0.5\; M$ solution of the electrolyte in $S \;m^2 mol^{-1}$ is:

asked Dec 11, 2018 by pady_1

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The metal that cannot be obtained by electrolysis of an aqueous solution of its salts is:

asked Dec 11, 2018 by pady_1

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If Z is a compressibility factor, van der Waals equation at low pressure can be written as:

asked Dec 11, 2018 by pady_1

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Which one of the following properties is not shown by NO?

asked Dec 11, 2018 by pady_1

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If $x = -1$ and $x = 2$ are extreme points of $f(x) = \alpha \log |x| + \beta x^2 + x$, then

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1 answer

The slope of the line touching both the parabolas $y^2 = 4x$ and $x^2 = -32y$ is

asked Dec 11, 2018 by pady_1

1 answer

The angle between the lines whose direction cosines satisfy the equations $l + m + n = 0$ and $l^2 = m^2 + n^2$ is

asked Dec 11, 2018 by pady_1

1 answer

If $(10)^9 + 2(11)^1 (10)^8 + 3(11)^2 (10)^7 + ....+ 10(11)^9 = k(10)^9$, then $k$ is equal to

asked Dec 11, 2018 by pady_1

1 answer

Three positive numbers from an increasing G.P. If the middle term in this G.P. is doubled, the new numbers are in A.P. Then the common ratio of the G.P. is

asked Dec 11, 2018 by pady_1

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The locus of the foot of perpendicular drawn from the centre of the ellipse $x^2 + 3y^2 = 6$ on any tangent to it is

asked Dec 11, 2018 by pady_1

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If $X = \{4^n - 3n - 1 : n \in N\}$ and $Y = \{9(n - 1) : n \in N\}$, where $N$ is the set of natural numbers, then $X \cup Y$ is equal to

asked Dec 11, 2018 by pady_1

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$\displaystyle{\lim_{x \to 0} \frac{\sin( \pi \cos^2 x)} {x^2}}$ is equal to

asked Dec 11, 2018 by pady_1

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Let PS be the median of the triangle with vertices $P(2, 2), Q(6, -1)$ and $R(7, 3)$. The equation of the line passing through $(1, -1)$ and parallel to PS is

asked Dec 11, 2018 by pady_1

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Let $a, b, c$ and d be non-zero numbers. If the point of intersection of the lines $4ax + 2ay + c = 0$ and $5bx + 2by + d = 0$ lies in the fourth quadrant and is equidistant from the two axes then

asked Dec 11, 2018 by pady_1

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The area of the region described by $A = \{(x, y) : x^2 + y^2 \leq 1$ and $y^2 \leq 1 - x\}$ is

asked Dec 11, 2018 by pady_1

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