Recent questions tagged 2009

$Al_2O_3$ is reduced by electrolysis at low potentials and high currents. If $4.0\times10^{4}$ amperes of current is passed through molten $Al_2O_3$ for 6 hours, what mass of aluminium is produced ? (Assume 100% current efficiency, at. mass of$ Al = 27 g mol^{–1}$) -

asked Jul 26, 2018 by pady_1

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Which of the following oxides is not expected to react with sodium hydroxide ?

asked Jul 26, 2018 by pady_1

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In the case of alkali metals, the covalent character decreases in the order :

asked Jul 26, 2018 by pady_1

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According to MO theory which of the following lists ranks the nitrogen species in terms of increasing bond order :

asked Jul 26, 2018 by pady_1

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Among the following which is the strongest oxidizing agent ? -

asked Jul 26, 2018 by pady_1

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In which of the following molecules / ions $BF_3,NO{_2}{^-},NH{_2}{^-},H{_2}$ and the central atom is $sp^2$ hybridized ?

asked Jul 26, 2018 by pady_1

1 answer

A 0.0020 M aqueous solution of an ionic compound $Co(NH_3)_5(NO_2)Cl $ freezes at $- 0.00732^ºC$. Number of moles of ions which 1 mole of ionic compound produces on being dissolved in water will be : ($k_f = 1.86^ºC/m$)

asked Jul 26, 2018 by pady_1

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The equivalent conductance of $\frac {M}{32}$ solution of a weak monobasic acid is 8.0 mho $cm ^2$ and at infinite dilution is 400 mho $cm ^2$, The dissociation constant of this acid is -

asked Jul 26, 2018 by pady_1

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For the reaction $A + B\rightarrow$products, it is observed that : <br> (1) On doubling the initial concentration of A only, the rate of reaction is also doubled and <br> (2) On doubling the initial concentration of both A and B, there is a change by a factor of 8 in the rate of the reaction. <br> The rate of this reaction is given by :

asked Jul 26, 2018 by pady_1

1 answer

For the reaction, $N_2+3H_2\to 2NH_3$, $\frac {d[NH_3]}{dt}=2\times10^{-4} mol L^{-1} S^{-1}$, The value of $\frac{-d[H_2]}{dt}$ would be

asked Jul 26, 2018 by pady_1

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Which of the following is not permissible arrangement of electrons in an atom ?

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Maximum number of electrons in a subshell or an atom is determined by the following :

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Oxidation number of P in $PO_{4}^{3-}$, of S in $SO_{4}^{2-}$and that of Cr in $Cr_{2}O_{7}^{2-}$ are respectively :

asked Jul 26, 2018 by pady_1

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10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. Amount of water produced in this reaction will be -

asked Jul 26, 2018 by pady_1

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A transistor is operated in common-emitter configuration at $V_c=2V$ such that a change in the base current from 100 µA to 200 µA produces a change in the collector current from 5 mA to 10 mA. The current gain is :

asked Jul 26, 2018 by pady_1

2 answers

In a Rutherford scattering experiment when a projectile of charge $Z_1 $ and mass $M_1$ approaches a target nucleus of charge $Z_2 $ and mass $M_2 $, the distance of closest approach is $r_0 $. The energy of the projectile is :

asked Jul 26, 2018 by pady_1

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The ionization energy of the electron in the hydrogen atom in its grounds state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between :

asked Jul 26, 2018 by pady_1

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The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an :

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A student measures the terminal potential difference (V) of a cell (of emf $\epsilon$ and internal) resistance r) as a function of the current (I) 0 flowing through it. The slope and intercept of the graph between V and I, then respectively equal to :

asked Jul 26, 2018 by pady_1

1 answer

Three concentric spherical shells have radii a, b, and c(a < b < c) and have surface charge densities $\sigma$,$-\sigma$ and $\sigma$ respectively. If $V_A,V_B,V_C$ denote the potentials of the three shells, then, for c = a + b, we have :

asked Jul 26, 2018 by pady_1

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Power dissipated in an LCR series circuit connected to an a.c. source of emf ? is : 2

asked Jul 26, 2018 by pady_1

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Under the influence of a uniform magnetic field, a charged particle moves with constant speed V in a circle of radius R. The time period of rotation of the particle :

asked Jul 26, 2018 by pady_1

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The magnetic force acting on a charged particle a of charge – 2µc in a magnetic field of 2T acting in y direction, when the particle velocity is $(2\widehat{i} + 3\widehat{j})\times 10^5ms^-1$, is :

asked Jul 26, 2018 by pady_1

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A bar magnet having a magnetic movement of $2\times10^4 JT^{-1}$ is free to rotate in a horizontal plane. A horizontal magnetic field $B=6\times10^{-4}T$ exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60º from the field is :

asked Jul 26, 2018 by pady_1

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A wire of resistance 12 ohms per metre is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points, A and B as shown in the figure, is :

asked Jul 26, 2018 by pady_1

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Three capacitors each of capacitance C and of breakdown voltage V are joined in series. The capacitance and breakdown voltage of the combination will be :

asked Jul 26, 2018 by pady_1

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Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same and equal to 1 g/m. When both the strings vibrate simultaneously the number of beats is :

asked Jul 26, 2018 by pady_1

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The driver of a car traveling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is :

asked Jul 26, 2018 by pady_1

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The internal energy change in a system that has absorbed 2 k cal of heat and done 500 J of work is :

asked Jul 26, 2018 by pady_1

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A black body at $227^{\circ}C$ radiates heat at the rate of $7cals/cm^{2}s$. At a temperature of $727^{\circ}C$, the rate of heat radiated in the same units will be :

asked Jul 26, 2018 by pady_1

1 answer

In thermodynamic processes which of the following statements is not true ?

asked Jul 26, 2018 by pady_1

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The two ends of a rod of length L and a uniform cross-sectional area A are kept at two temperatures $T_1$ and $T_2$ $(T_1>T_2)$. The rate of heat transfer, $\frac{dQ}{dt}$ through the rod in a steady dt state is given by :

asked Jul 26, 2018 by pady_1

1 answer

A thin circular ring of mass M and radius R is rotating in a horizontal plane about an axis vertical to its plane with a constant angular velocity $\omega$, If two objects each mass m be attached gently to the opposite ends of a f diameter of the ring, the ring, will then rotate with an angular velocity :

asked Jul 26, 2018 by pady_1

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Four identical thin rods each of mass M and length l, from a square frame. Moment of inertia of this frame about an axis through the centre of the square and perpendicular to its plane is :

asked Jul 26, 2018 by pady_1

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Two bodies of mass 1 kg and 3 kg have position vectors$\widehat{i}+2\widehat{j}+\widehat{k}$ and $-3\widehat{i}-2\widehat{j}+\widehat{k}$ , respectively. The centre of mass of this system has a position vector :

asked Jul 26, 2018 by pady_1

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A block of mass M is attached to the lower end : of a vertical spring. The spring is hung from a ceiling and has force constant value k. The mass is released from rest with the spring initially unstretched. The maximum extension produced in the length of the spring will be :

asked Jul 26, 2018 by pady_1

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Transgenic plants are the ones -

asked Jul 26, 2018 by pady_1

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Polyethylene glycol method is used for :

asked Jul 26, 2018 by pady_1

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Which one of the following pairs is wrongly matched ?

asked Jul 26, 2018 by pady_1

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The bacterium Bacillus thuringiensis is widely used in contemporary biology as -

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which one of the following is commonly used in transfer of foreign DNA into crop plants ?

asked Jul 26, 2018 by pady_1

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Alzhimer disease in humans is associated with the deficiency of :

asked Jul 26, 2018 by pady_1

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Use of anti-histamines and steroids give a quick relief from -

asked Jul 26, 2018 by pady_1

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Which one is the wrong pairing for the disease and its causal organism ?

asked Jul 26, 2018 by pady_1

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Somaclones are obtained by : -

asked Jul 26, 2018 by pady_1

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Global agreement in specific control strategies to reduce the release of ozone depleting substances, was adopted by :

asked Jul 26, 2018 by pady_1

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DDT residues are rapidly passed through food chain causing biomagnification because DDT is :

asked Jul 26, 2018 by pady_1

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Biochemical Oxygen Demand (BOD) in a river water :

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Step taken by the Government of India to control air pollution include :

asked Jul 26, 2018 by pady_1

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Chipko movement was launched for the protection of -

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