Practice Questions

Q28.A circular conducting coil of radius 1 m is being heated by the change of magnetic field →𝐵 passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2 μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as 4 𝑡 𝐵= 𝜋× 10-3 𝑇1 - 100 The energy dissipated by the coil before the magnetic field is switched off completely is 𝐸= ______mJ.

Q28.Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective cases is x : 3 The value of x is

Q28.Seawater at a frequency f = 9 × 102 Hz , has permittivity ε = 80ε0 and resistivity ρ = 0. 25 Ω m . Imagine a parallel plate capacitor is immersed in seawater and is driven by an alternating voltage source V (t) = V0 sin(2πft). Then the conduction current density becomes 10x times the displacement current density after time t = 8001 s. The value of x is _______ (Given : 1 = 9 × 109 N m2 4πε0 C−2)

Q28.A radioactive sample has an average life of 30 ms and is decaying. A capacitor of capacitance 200 μF is first charged and later connected with resistor R. If the ratio of the charge on the capacitor to the activity of the radioactive sample is fixed with respect to time then the value of R should be _______Ω.

Q28.An object is placed at a distance of 12 cm from a convex lens. A convex mirror of focal length 15 cm is placed on another side of the lens at 8 cm as shown in the figure. The image of the object coincides with the object. When the convex mirror is removed, a real and inverted image is formed at a position. The distance of the image from the object will be ___ cm JEE Main 2021 (26 Aug Shift 2) JEE Main Previous Year Paper

Q29.The Kα X-ray of molybdenum has wavelength 0. 071 nm. If the energy of a molybdenum atom with a K electron knocked out is 27. 5 keV, the energy of this atom when an L electron is knocked out will be keV. (Round off to the nearest integer ) [h = 4. 14 × 10−15 eV s, c = 3 × 108 m s−1]

Q29.An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification 6, gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0. 6 m, if the focal length of the eyepiece is equal to ____ cm.

Q29.Two satellites revolve around a planet in coplanar circular orbits in anticlockwise direction. Their period of revolutions are 1 hour and 8 hours respectively. The radius of the orbit of nearer satellite is 2 × 103 km . The angular speed of the farther satellite as observed from the nearer satellite at the instant when both the satellites are closest is 𝜋 h-1, where 𝑥 is _______ . 𝑥rad

Q30.A deviation of 2° is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass are 0. 02 and 0. 03 respectively and refractive JEE Main 2021 (16 Mar Shift 2) JEE Main Previous Year Paper index for yellow light for these glasses are 1. 5 and 1. 6 respectively. The refracting angles for crown glass prism will be ________ ° (in degree) (Round off to the Nearest Integer)

Q30.A particle of mass m moves in a circular orbit in a central potential field U(r) = U0r4. If Bohr's quantization α , where α is _______ . conditions are applied, radii of possible orbitals rn vary with n 1

Q31.Complete combustion of 1. 80 g of an oxygen containing compound (CxHyOz) gave 2. 64 g of CO2 and 1. 08 g of H2O. The percentage of oxygen in the organic compound is : (1) 53. 33 (2) 50. 33 (3) 51. 63 (4) 63. 53

Q54.The number of moles of NH3, that must be added to 2 L of 0. 80 MAgNO3 in order to reduce the concentration of Ag+ ions to 5. 0 × 10−8M(Kformation for [Ag (NH3)2]+ = 1. 0 × 108) is __________. (Nearest integer) [Assume no volume change on adding NH3 ]

Q54.The OH− concentration in a mixture of 5. 0 mL of 0. 0504 M NH4 Cl and 2 mL of 0. 0210 M NH3 solution is x × 10−6 M . The value of x is (Nearest integer) [Given Kw = 1 × 10−14 and Kb = 1. 8 × 10−5]

Q55.For the reaction A + B ⇌2C the value of equilibrium constant is 100 at 298 K. If the initial concentration of all the three species is 1 M each, then the equilibrium concentration of C is x × 10-1 M. The value of x is _______. (Nearest integer)

Q55.In basic medium CrO2−4 oxidises S2O2−3 to form SO4 2− and itself changes into Cr (OH)−4 .The volume of 0. 154 MCrO2−4 required to react with 40 mL of 0. 25 MS2 O3 2− is _____ mL. (Rounded-off to the nearest integer)

Q56.Consider the following cell reaction Cd(s) + Hg2 SO4( s) + 95 H2O(l) ⇌CdSO4 ⋅95 H2O(s) + 2 Hg(l). The value of E0cell is 4. 315 V at 25°C. If ΔH°= −825. 2 kJ mol−1, the standard entropy change ΔS° in J K−1 is _________ . (Nearest integer) [Given : Faraday constant = 96487 C mol−1 ]

Q56. Ga (atomic mass 70 u ) crystallizes in a hexagonal close packed structure. The total number of voids in 0. 581 g of Ga is ________ ×1021 . (Round off to the Nearest Integer).

Q56.A solute A dimerizes in water. The boiling point of a 2 molal solution of A is 100. 52∘C. The percentage association of A is ___ . (Round off to the Nearest integer) Use : Kb for water = 0. 52 K kg mol−1 Boiling point of water = 100°C

Q56.A 1 molal K4 Fe(CN)6 solution has a degree of dissociation of 0. 4 . Its boiling point is equal to that of another solution which contains 18. 1 weight percent of a non electrolytic solute A . The molar mass of A is _____ u. (Round off to the Nearest Integer). [Density of water = 1. 0 g cm−3]

Q57.Copper reduces NO−3 into NO and NO2 depending upon the concentration of HNO3 in solution. (Assuming fixed [Cu2+] and PNO = PNO2 ), the HNO3 concentration at which the thermodynamic tendency for reduction of NO−3 into NO and NO2 by copper is same is 10x M. The value of 2x is ___. (Rounded-off to the nearest integer) [Given, Eo = 0. 34 V, Eo = 0. 96 V, Eo = 0. 79 V and at 298 K, RTF (2. 303) = 0. 059] Cu2+ / Cu NO−3 / NO NO−3 / NO2

Q57.Consider the following reaction MnO−4 + 8H+ + 5e−→Mn+2 + 4H2O , E°= 1. 51 V The quantity of electricity required in Faraday to reduce five moles of MnO−4 is

Q58.For the cell Cu(s) Cu2+(aq)(0. 1M)∥Ag+(aq)(0. 01M) Ag(s) the cell potential E1 = 0. 3095 V . For the cell Cu(s) Cu2+(aq)(0. 01M)∥Ag+(aq)(0. 001M) Ag(s) the cell potential = x × 10−2 V. Find value of x (Round off the Nearest Integer). [ Use : 2.303F RT = 0. 059 J ]

Q58.Sucrose hydrolyses in acid solution into glucose and fructose following first order rate law with a half-life of 3. 33 h at 25°C. After 9 h, the fraction of sucrose remaining is f. The value of log10( 1f ) is ________ ×10−2. (Rounded off to the nearest integer) [Assume: In 10 = 2. 303, ln 2 = 0. 693]

Q59. A and B decompose via first order kinetics with half-lives 54. 0 min and 18. 0 min respectively. Starting from an equimolar non-reactive mixture of A and B, the time taken for the concentration of A to become 16 times that of B is ______ min. (Round off to the Nearest Integer). Q60. [Ti (H2O)6]3+ absorbs light of wavelength 498 nm during a d −d transition. The octahedral splitting energy for the above complex is _______ ×10−19 J. (Round off to the Nearest Integer). h = 6. 626 × 10−34 Js; c = 3 × 108 ms−1 .

Q59.Consider the cell at 25°C ZnZn2 + aq, 1 M‖Fe3 + (aq), Fe2 + aqPts The fraction of total iron present as Fe3 + ion at the cell potential of 1 . 500 V is x × 10-2. The value of x is ______. (Nearest integer) Given: E∘ + + = 0 . 77V, E∘ + = - 0 . 76V Fe3 | Fe2 Zn2 | Zn