Recent questions in JEEMAIN PAST PAPERS

Which of the following compounds will form significant amount of meta product during mono-nitration reaction ?

asked Dec 11, 2018 by pady_1

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The products obtained when chlorine gas reacts with cold and dilute aqueous NaOH are :

asked Dec 11, 2018 by pady_1

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The correct sequence of reagents for the following conversion will be :

asked Dec 11, 2018 by pady_1

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Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect, is :

asked Dec 11, 2018 by pady_1

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The increasing order of the reactivity of the following halides for the $S_N1$ reaction is :

asked Dec 11, 2018 by pady_1

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$pK_a$ of a weak acid (HA) and $pK_b$ of a weak base $(BOH)$ are $3.2$ and $3.4$, respectively. The pH of their salt (AB) solution is :

asked Dec 11, 2018 by pady_1

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On treatment of $100 \;mL$ of $ 0.1 \;M$ solution of $CoCl_3.6H_2O$ with excess $AgNO_3;\; 1.2 \times 10^{22}$ ions are precipitated. The complex is :

asked Dec 11, 2018 by pady_1

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Which of the following species is not paramagnetic?

asked Dec 11, 2018 by pady_1

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The major product obtained in the following reaction is :

asked Dec 11, 2018 by pady_1

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Whcih of the following compounds will behave as a reducing sugar in an aqueous KOH solution?

asked Dec 11, 2018 by pady_1

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In the following reactions, $ZnO$ is respectively acting as a/an : (a) $ZnO + Na_2O \to Na_2ZnO_2$ (b) $ZnO + CO_2 \to ZnCO_3$

asked Dec 11, 2018 by pady_1

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The Tyndall effect is observed only when following conditions are satisfied : (a) The diameter of the dispersed particles is much smaller than the wavelength of the light used. (b) The diameter of the dispersed particles is not much smaller than the wavelength of the light used (c) The refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude. (d) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.

asked Dec 11, 2018 by pady_1

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Given : $E^{\circ}_{Cl_2/Cl^-} = 136 \; V, \; \; \; E^{\circ}_{Cr^{3+} / Cr} = -0.74 \; V$ $E^{\circ}_{Cr_2O_7^{2-}/Cr^{3+}} = 1.33\; V, \; \; \; E^{\circ}_{MnO_4^- / Mn^{2+}} = 1.51 \; V$ Among the following, the strongest reducing agent is :

asked Dec 11, 2018 by pady_1

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The formation of which of the following polymers involves hydrolysis reaction ?

asked Dec 11, 2018 by pady_1

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$\Delta U$ equal to :

asked Dec 11, 2018 by pady_1

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The most abundant elements by mass in the body of a healthy human adult are : Oxygen (61.4%); Carbon (22.9%), Hydrogen (10.0%) ; and Nitrogen (2.6%). The weight which a 75 kg person would gain if all $^1H$ atoms are replaced by $^2H$ atoms is :

asked Dec 11, 2018 by pady_1

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The freezing point of benzene decreases by $0.45^{\circ}C$ when $0.2\; g$ of acetic acid is added to $20 \;g$ of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be : $(K_f$ for benzene = $5.12\; K \;kg\; mol^{–1} )$

asked Dec 11, 2018 by pady_1

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Given : $C_(graphite) + O_2(g) \to CO_2 (g) ; \; \; \; \; \Delta_r H^{\circ} = -393.5\; kJ \; mol^{-1};$ $H_2(g) + \frac{1}{2}O_2(g) \to H_2O(l); \;\;\;\; \; \; \; \; \Delta_rH^{\circ} = -285.8 \; kJ\; mol^{-1};$ $CO_2(g) + 2 H_2O (l) \to CH_4(g) + 2O_2 (g); \; \; \; \; \Delta_r H^{\circ} = + 890.3 \;kJ\; mol^{-1}$ Based on the above thermochemical equations, the value of $\Delta_r H^{\circ}$ at 298 K for the reaction

asked Dec 11, 2018 by pady_1

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1 gram of a carbonate $(M_2CO_3)$ on treatment with excess HCl produces $0.01186 \;mole$ of $CO_2$. The molar mass of $M_2CO_3$ in $g\; mol^{–1}$ is :

asked Dec 11, 2018 by pady_1

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A body of mass $m = 10^{-2} kg$ is moving in a medium and experiences a frictional force $F= -kv^2$. Its initial speed is $v_0 = 10\; ms^{-1}$. If after 10 s, its energy is $\frac{1}{8} mv_0^2$, the value of $k$ will be :

asked Dec 11, 2018 by pady_1

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A diverging lens with magnitude of focal length 25cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is :

asked Dec 11, 2018 by pady_1

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An external pressure P is applied on a cube at $0^{\circ}C$ so that it is equally compressed from all sides. $K$ is the bulk modulus of the material of the cube and $\alpha$ is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by :

asked Dec 11, 2018 by pady_1

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The variation of acceleration due to gravity g with distance d from centre of the earth is best represented by (R = Earth's radius)

asked Dec 11, 2018 by pady_1

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When a current of $5 \;mA$ is passed through a galvanometer having a coil of resistance $15 \; \Omega$, it shows full scale defection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range $0 – 10\; V$ is :

asked Dec 11, 2018 by pady_1

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A man grows into a giant such that his linear dimensions increase by a factor of 9. Assuming that his density remains same, the stress in the leg will change by factor of :

asked Dec 11, 2018 by pady_1

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An observer is moving with half the speed of light towards stationary microwave source emitting waves at frequency $10\;GHz$. What is the frequency of the microwave measured by the observer ? (speed of light = $3 \times 10^8\;ms^{–1}$ )

asked Dec 11, 2018 by pady_1

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A particle is executing simple harmonic motion with a time period T. At time = 0, it is at its position of equilibrium. The kinetic energy-time graph of the particle will look like :

asked Dec 11, 2018 by pady_1

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Which of the following statements is false ?

asked Dec 11, 2018 by pady_1

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In the given circuit diagram when the current reaches steady state in the circuit, the charge on the capacitor of capacitance C will be :

asked Dec 11, 2018 by pady_1

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In the given circuit diagram when the current reaches steady state in the circuit, the charge on the capacitor of capacitance C will be :

asked Dec 11, 2018 by pady_1

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A capacitance of $2 \mu F$ is required in an electrical circuit across a potential difference of $1.0\; kV$. A large number of $1 \mu F$ capacitors are available which can withstand a potential difference of not more than $300\; V$. The minimum number of capacitors required to achieve this is :

asked Dec 11, 2018 by pady_1

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A body is thrown vertically upwards. Which one of the following graphs correctly represent the velocity vs time ?

asked Dec 11, 2018 by pady_1

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In the above circuit the current in each resistance is :

asked Dec 11, 2018 by pady_1

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Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths $r = \lambda_1/\lambda_2$, is given by :

asked Dec 11, 2018 by pady_1

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A time dependent force F = 6t acts on a particle of mass 1kg. If the particle starts from rest, the work done by the force during the first 1 sec. will be :

asked Dec 11, 2018 by pady_1

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In a coil resistance $100 \Omega$, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is :

asked Dec 11, 2018 by pady_1

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An electric dipole has a fixed dipole moment $\overrightarrow{p}$, which makes angle $\theta$ with respect to x-axis. When subjected to an electric field $\overrightarrow{E_1} = E \hat{i}$, it experiences a torque $\overrightarrow{T_1} = \tau \hat{k}$. When subjected to another electric field $\overrightarrow{E_2} = \sqrt{3} E_1 \hat{j}$ it experiences a torque $\overrightarrow{T_2} = - \overrightarrow{T_1}$. The angle $\theta$ is :

asked Dec 11, 2018 by pady_1

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A magnetic needle of magnetic moment $6.7 \times 10^{-2} \; Am^2$ and moment of inertia $7.5 \times 10^{-6} kg\;m^2$ is performing simple harmonic oscillations in a magnetic field of $0.001\; T$. Time taken for $10$ complete oscillations is :

asked Dec 11, 2018 by pady_1

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A particle A of mass m and initial velocity $v$ collides with a particle B of mass $\frac{m}{2}$ which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths $\lambda_A$ to $\lambda_B$ after the collision is :

asked Dec 11, 2018 by pady_1

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In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is :

asked Dec 11, 2018 by pady_1

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The temperature of an open room of volume $30 \;m^3$ increased from $17^{\circ}C$ to $27^{\circ}C$ due to the sunshine. The atmospheric pressure in the room remains $1 \times 10^5 \; Pa$. If $n_i$ and $n_f$ are the number of molecules in the room before and after heating, then $n_f – n_i$ will be :

asked Dec 11, 2018 by pady_1

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In amplitude modulation, sinusoidal carrier frequency used is denoted by $\omega_c$ and the signal frequency is denoted by $\omega_m$. The bandwidth $(\Delta \omega_m)$ of the signal is such that $\Delta \omega_m<< \omega_c$. Which of the following frequency is not contained in the modulated wave ?

asked Dec 11, 2018 by pady_1

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A copper ball of mass $100\; gm$ is at a temperature T. It is dropped in a copper calorimeter of mass $100 \;gm$, filled with $170\; gm$ of water at room temperature. Subsequently, the temperature of the system is found to be $75^{\circ} C$. T is given by : (Given : room temperature = $30^{\circ}C$, specific heat of copper = $0.1 \;cal/gm^{\circ}C$)

asked Dec 11, 2018 by pady_1

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$C_p$ and $C_v$ are specific heats at constant pressure and constant volume respectively. It is observed that $C_p - C_v$ = a for hydrogen gas $ C_p - C_v$ = b for nitrogen gas The correct relation between a and b is :

asked Dec 11, 2018 by pady_1

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A slender uniform rod of mass M and length l is pivoted at one end so that it can rotate in a vertical plane (see figure). There is negligible friction at the pivot. The free end is held vertically above the pivot and then released. the angular acceleration of the rod when it makes an angle $\theta$ with the vertical is

asked Dec 11, 2018 by pady_1

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The moment of inertia of a uniform cylinder of length $l$ and radius $R$ about its perpendicular bisector is $I$. What is the ratio $l/R$ such that the moment of inertia is minimum ?

asked Dec 11, 2018 by pady_1

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An electron bean is acceleration by a potential difference $V$ to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays. If $\lambda_{min}$ is the smallest possible wavelength of X-ray in the spectrum, the variation of log $\lambda_{min}$ with $\log\; V$ is correctly represented in :

asked Dec 11, 2018 by pady_1

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The following observations were taken for determining surface tension T of water by capillary method : diameter of capillary, $D = 1.25 \times 10^{–2}$ m rise of water , $h = 1.45 \times 10^{–2} m$. Using $ g = 9.80\; m/s^2$ and the simplified relation $T = \frac{rhg}{2} \times 10^3\; N/m$, the possible error in surface tension is closest to :

asked Dec 11, 2018 by pady_1

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A radioactive nucleus A with a half life T, decays into a nucleus B. At t = 0, there is no nucleus B. At sometime t, the ratio of the number of B to that of A is 0.3. Then, t is given by :

asked Dec 11, 2018 by pady_1

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The integral $\begin{align} \int^{\frac{3\pi}{4}}_{\frac{\pi}{4}} \frac{dx}{1+ \cos x} \end{align}$ is equal to

asked Dec 11, 2018 by pady_1

1 answer

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