Recent questions in JEEMAIN PAST PAPERS

Two solutions of a substance (non electrolyte) are mixed in the following manner. 480 mL of 1.5 M first solution + 520 mL of 1.2 M second solution. What is the molarity of the final mixture ?

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A reaction involving two different reactants can never be

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Hydrogen ion concentration in mol/L in a solution of pH = 5.4 will be :

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The exothermic formation of $ClF_3$ is represented by the equation : $Cl_2 (g) + 3F_2 (g) \leftrightharpoons 2 ClF_3 (g); \Delta Hr = -329 kJ$. Which of the following will increase the quantity of $ClF_3$ in an equilibrium mixture of $Cl_2, F_2 $ and $ClF_3$?

asked Nov 5, 2018 by pady_1

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For the reaction $2NO_2 (g) \rightleftharpoons 2 NO (g) + O_2(g)$ ($K_c = 1.8 \times 10^{-6}$ at $ 184^{\circ} $ C ) ($R = 0.00831\; k J/(mol.K)$ ) When $K_p$ and $K_c$ are compared at $184^{\circ} C$ it is found that :

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Which one of the following statements is not true about the effect of an increase in temperature on the distribution of molecular speeds in a gas ?

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Benzene and toluene form nearly ideal solutions. At $20^{\circ}C$, the vapour pressure of benzene is 75 torr and that of toluene is 22 torr. The partial vapour pressure of benzene at $20^{\circ} C$ for a solution containing 78 g of benzene and 46 g of toluene in torr is :

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The solubility product of a salt having general formula $MX_2$, in water is $4 \times 10^{-12}$. The concentration od $M^{2+}$ ions in the aqueous solution of the salt is :

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Consider the reaction : $N_2 + 3H_2 \to 2NH_3$ carried out at constant temperature and pressure. If $\Delta H$ and $\Delta U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true ?

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The volume of a colloidal particle, $V_C$ as compared to the volume of a solute particle in a true solution $V_S$ could be :

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Aluminium oxide may be electrolysed at $1000^{\circ} C$ to furnish aluminium metal (Atomic mass =27 amu; 1 faraday= 96,500 Coulombs). The cathode reaction is $Al^{3+} + 3e^- \to Al^0$ To prepare 5.12 Kg of aluminium metal by this method would require :

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Consider an endothermic reaction $X \to Y$ with the activation energies $E_b$ and $E_f$ for the backwarrd and forward reactions respectively. In general :

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Lattice energy of an ionic compound depends upon :

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The highest electrical conducitivity of the following aqueous solutions is of :

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An ionic compound has a unit cell consisting of A ions at the corners of a cube and B ions on the centres of the faces of the cube. The empirical formula for this compound would be :

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Hydrogen bomb is based on the principle of :

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For a spontaneous reaction the $\Delta G$, equilibrium constant $(K)$ and $E_{cell}^{\circ}$ will be respectively :

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Due to the presence of an unpaired electron free radicals are :

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Which of the following is a polyamide ?

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If $\alpha$ is the degree of dissociation of $Na_2SO_4$, the van't Hoff factor ($i$) used for calculating the molecular mass is :

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Which one of the following species is diamagnetic in nature ?

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Which of the following oxides is amphoteric in character ?

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Which one of the following types of drugs reduces fever ?

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The oxidation state of $Cr$ in $[Cr(NH_3)_4 Cl_2]^+$ is :

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A magnetic needle is kept in a non-uniform magnetic field. It experiences :

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The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp, when not in use ?

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In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of $ 2 \Omega$, the balancing length becomes 120 cm. The internal resistance of the cell is :

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A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The time taken by the particle of complete one revolution is :

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The uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then :

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The phase difference between the alternating current and emf is $\pi/2$. Which of the following cannot be the constituent of the circuit ?

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A circuit has a resistance of $12 \Omega$ and an impedance of $15 \Omega$. The power factor of the circuit will be :

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An energy source will supply a constant current into the load, if its internal resistance is :

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The self-inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of :

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A coil of inductance 300 mH and resistance $2 \Omega $ is connected to a source of voltage $2V$. The current reaches half of its steady state value in :

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Two concentric coils each of radius equal to $2 \pi$ cm are placed at right angles to each other. 3A and 4A are the currents flowing in each coil respectively. The magnetic induction in $Wb/m^2$ at the centre of the coils will be : ($\mu_0 = 4 \pi \times 10^{-7} \; Wb/Am$)

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If $I_0$ is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled ?

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An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency ?

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The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would :

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If a simple harmonic motion is represented by $\frac{d^2x}{dt^2} + \propto x = 0$, its time peroid is :

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When two tuning forks (fork 1 and fork 2) are sounded simultaneously, 4 beats per second are heard. Now, some tape is attached on the prong of the fork 2. When the tuning forks are sounded again, 6 beats per second are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2 ?

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A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C, then the resultant capacitance is :

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Two thin wire rings each having a radius R are placed at a distance d apart with their axes coinciding. The charges on the two rings are $+q$ and $-q$. The potential difference between the centres of the two rings is :

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Two point charges $+8 q$ and $-2q$ are located at $x=0$ and $x=L$ respectively. The location of a point on the $x$-axis at which the net electric field due to these two point charges is zero is :

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A charged ball B hangs from a silk thread S, which makes an angle $\theta$ with a large charged conducting sheet P, as shown in the figure. The surface charge density $\sigma$ of the sheet is proportional to :

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When an unpolarized light of intensity $I_0$ is incident on a polarizing sheet, the intensity of the light which does not get transmitted is:

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Two thin, long, parallel wires, separated by a distance $d$ carry $a$ current of $i$ $A$ in the same direction. They will :

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A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be :

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One conducting U-tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed $\nu$, then the emf induced in the circuit in terms of $B, l$ and $\nu$, where $l$ is the width of each tube, will be :

asked Nov 5, 2018 by pady_1

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A fully charged capacitor has a capacitance $C$. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity $s$ and mass $m$. If the temperature of the block is raised by $\Delta T$, the potential difference $V$ across the capacitance is :

asked Nov 5, 2018 by pady_1

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Two sources of equal emf are connected to an external resistance $R$. The internal resistances of the two sources are $R_1$ and $R_2 (R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$, is zero, then :

asked Nov 5, 2018 by pady_1

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