Recent questions tagged 2007

In which of the following pairs, the two species are iso-structural ?

asked Jul 26, 2018 by pady_1

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Identify the correct order of the size of the following :

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The fraction of total volume occupied by the atoms present in a simple cube is :

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A weak acid HA has a $K_a$ of $1.00 \times 10^{-5}$. If $0.100\; mol $ of this acid is dissolved in one litre of water the percentage of acid dissociated at equilibrium is closest to :

asked Jul 26, 2018 by pady_1

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Calculate the pOH of a solution at $25^{\circ} C$ that contains $1 \times 10^{-10} M$ of hydronium ions, i.e. $H_3O^+$;

asked Jul 26, 2018 by pady_1

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The following equilibrium constants are given - The equilibrium constant for the oxidation of $NH_3$ by oxygen to give $NO$ is :

asked Jul 26, 2018 by pady_1

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The Langmuir adsorption isotherm is deduced using the assumption :

asked Jul 26, 2018 by pady_1

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Given that bond energies of $H-H$ and $Cl-Cl$ are 430 $kJ mol^{-1}$ and 240 $kJ mol^{-1}$ respectively and $\Delta_f H$ for $HCl$ is -90 $kJ mol^{-1}$. Bond enthalpy of $HCl$ is :

asked Jul 26, 2018 by pady_1

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Consider the following reactions : $(a) \; H^+_{(aq)} + OH^- _{(aq)} = H_2O_{(l)}, \Delta H = -X_1kJ\; mol^{-1}$ $(b)\; H_{2(g)} + \frac{1}{2} O_{2(g)} = H_2O_{(l)}, \Delta H = -X_2 kJ mol^{-1} $ $(c)\; CO_{2(g)} + H_{2(g)} = CO_{(g)} + H_2O_{(l)} -X_3 kJ mol^{-1}$ $(d)\; C_2H_{2(g)} + \frac{5}{2} O_{2(g)} = 2CO_{2(g)} + H_2O_{(l)} +X_4 kJ mol^{-1}$ Enthalpy of formation of $H_2O_{(l)} $ is:

asked Jul 26, 2018 by pady_1

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The efficiency of a fuel cell is given by :

asked Jul 26, 2018 by pady_1

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0.5 molal aqueous solution of a weak acid (HX) is $20 \%$ ionised. If $K_f$ for water is $1.86 K\; kg\; mol^{-1}$, the lowering in freezing point of the solution is :

asked Jul 26, 2018 by pady_1

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The equilibrium constant of the reaction : $Cu(s) + 2Ag^+(aq) \to Cu^{2+}(aq) +2Ag(s); $ $E^o = 0.46V$ at 298 K is :

asked Jul 26, 2018 by pady_1

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If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately : ($\log 4 = 0.60, \log 5 = 0.69$)

asked Jul 26, 2018 by pady_1

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The reaction of hydrogen an iodic monochloride is given as $H_{2(g)} +2ICl_{(g)} \to 2HCl_{(g)}+I_{2(g)} $ Mechanism B : $H_{2(g)} +ICl_{(g)} \to HCl_{(g)}+HI_{(g)} $; Slow $HI_{(g)} +ICl_{(g)} \to HCl_{(g)}+I_{2(g)} $; Fast Which of the above mechanism(s) can be consistent with the given information about the reaction :

asked Jul 26, 2018 by pady_1

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In a first order reaction $[A \to B$ ], if $k$ is rate constant and initial concentration of the reactant A is 0.5 M then the half-life is :

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The number of moles of $KMnO_4$ that will be needed to react with one mole of sulphite ion in acidic slution is :

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Consider the following sets of quantum number : Which of the following sets of quantum number is not possible :

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Concentrated aqueous sulphuric acid is $98\% H_2SO_4$ by mass and has a density of $1.80 g.mL^{-1} $ Volume of acid required to make 1 litre of $0.1 MH_2SO_4$ solution is :

asked Jul 26, 2018 by pady_1

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An element, X has the following isotopic composition; $^{200}X : 90 \%$ $^{199}X : 8.0 \%$ $^{202}X : 2.0 \%$ The weighted average atomic mass of the naturally - occurring element X is closest to :

asked Jul 26, 2018 by pady_1

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With which of the following electronic configuration of an atom has the lowest ionization enthalpy :

asked Jul 26, 2018 by pady_1

2 answers

For a cubic crystal structure which one of the following relations indicting the cell characteristic is correct :-

asked Jul 26, 2018 by pady_1

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In the following circuit, the output Y for all possible inputs A and B is expresed by the truth table :-

asked Jul 26, 2018 by pady_1

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A common emitter amplifier has voltage gain of 50, an input impedance of 100 $\Omega$ and an output impedance of 200 $\Omega$. The power gain of the amplifier is :-

asked Jul 26, 2018 by pady_1

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In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is :- <img src""/>

asked Jul 26, 2018 by pady_1

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The total energy of electron in the ground state of hydrogen atom is -13.6 eV. The kinetic energy of an electron in first excited state is :-

asked Jul 26, 2018 by pady_1

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Two radioactive substances A and B have decay constants $5 \lambda$ and $\lambda $ respectively. At $t=0$ they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be $(\frac{1}{e} )^2$ after a time interval :-

asked Jul 26, 2018 by pady_1

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A nucleus $^A_Z X$ has mass represented by $M(A,Z)$. If $M_p$ and $M_n$ denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then:

asked Jul 26, 2018 by pady_1

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In radioactive decay process, the negatively charged emitted $\beta$- particles are :-

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If the nucleus $^{27}_{13}Al$ has a nuclear radius of about 3.6 fm, the $^{125}_{52}Te$ would have its radius approximately as :-

asked Jul 26, 2018 by pady_1

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In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio $\frac{Charge\; on\; the ion}{mass\; of\; the\; ion}$ will be proportional to :-

asked Jul 26, 2018 by pady_1

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Monochromatic light of frequency $6.0 \times 10^{14}$ Hz is produced by a laser. The power emitted is $2 \times 10^{-3}$W. The number of photons emitted, on the average, by the source per second is :-

asked Jul 26, 2018 by pady_1

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A 5 watt source emits monochromatic light of wavelength 5000 Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0m, the number of photo electrons liberated will :

asked Jul 26, 2018 by pady_1

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Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature then it will show :-

asked Jul 26, 2018 by pady_1

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A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately-

asked Jul 26, 2018 by pady_1

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What is the value of inductance L for which the current is a maximum in a series LCR circuit with $C = 10 \mu F$ and $\omega = 1000^{-1}$

asked Jul 26, 2018 by pady_1

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The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux $\phi$ linked with the primary coil is given by $\phi = \phi_0 + 4t$, where $\phi$ is in webers, t is time in seconds and $\phi_0$ is a constant, the output voltage across the secondary coil is :

asked Jul 26, 2018 by pady_1

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A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. It the electric field is switched off, and the same magnetic field is maintained, the electrons move :

asked Jul 26, 2018 by pady_1

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A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment $\mu$ is given by:

asked Jul 26, 2018 by pady_1

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Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion-

asked Jul 26, 2018 by pady_1

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The resistance of an ammeter is $13 \Omega $ and its scale is graduated for a current upto $100$ amps. After and additional shunt has been connected to this ammeter it becomes possible to measure currents upto $750$ amperes by this meter. The value of shunt-resistance is-

asked Jul 26, 2018 by pady_1

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Three resistances P, Q, R each of $2 \Omega$ and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of $6 \Omega$ is connected in parallel to S the bridge gets balanced. What is the value of S ?

asked Jul 26, 2018 by pady_1

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If the cold junction of a thermo-couple is kept at $0^{\circ}C$ and the hot junction is kept at $T^{\circ}C$, then the relation between neutral temperature $(T_n)$ and temperature of inversion $(T_i)$ is:

asked Jul 26, 2018 by pady_1

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A steady current of $1.5$ amp flows through a copper voltameter for 10 minutes. If the electrochemical equivalent of copper is $30 \times 10^{–5}$ gm $coulomb^{–1}$, the mass of copper deposited on the electrode will be: -

asked Jul 26, 2018 by pady_1

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The total power dissipated in watts in the circuit shown here is :-

asked Jul 26, 2018 by pady_1

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Two condensers, one of capacity $C$ and the other of capacity $\frac{C}{2}$ , are connected to a V-volt battery, as shown- The work done in charging fully both the condensers is :

asked Jul 26, 2018 by pady_1

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Three point charges +q, –2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0,y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are:-

asked Jul 26, 2018 by pady_1

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A hollow cylinder has a charge q coulomb within it. If $\phi$ is the electric flux in units of voltmeter associated with the curved surface B, the flux linked with the plane surface A in units of voltmeter will be- <img src =""/>

asked Jul 26, 2018 by pady_1

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Charge +q and â€“q are placed at points A and B respectively which are at distance $2L$ apart, C is the midpoint between A and B. The work done in moving a charge + Q along the semicircle CRD is:-

asked Jul 26, 2018 by pady_1

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A small coin is resting on the bottom of a beaker filled with a liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface (see figure) How fast is the light traveling in the liquid ?

asked Jul 26, 2018 by pady_1

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The electric and magnetic field of an electromagnetic wave are:-

asked Jul 26, 2018 by pady_1

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