Practice Questions

Q24.A car is fitted with a convex side-view mirror of focal length 20 cm. A second car 2.8 m behind the first car is overtaking the first car at relative speed of 15 m/s. The speed of the image of the second car as seen in the mirror of the first one is : JEE Main 2011 JEE Main Previous Year Paper (1) 1 m/s (2) 10 m/s 15 (3) 15 m/s (4) 101 m/s

Q25.Direction: The question has a paragraph followed by two statements, Statement −1 and statement −2. Of the given four alternatives after the statements, choose the one that describes the statements. A thin air film is formed by putting the convex surface of a plane - convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film. Statement-1 : When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of π. Statement-2 : The centre of the interference pattern is dark. (1) Statement-1 is true, Statement-2 is true; (2) Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-2 is not the correct explanation of Statement-1. Statement-1. (3) Statement- 1 is false. Statement- 2 is true. (4) Statement-1 is true, Statement- 2 is false.

Q26.This question has Statement −1 and Statement −2. Of the four choices given after the statements, choose the one that best describes the two statements. Statement-1 : A metallic surface is irradiated by a monochromatic light of frequency v > v0 (the threshold frequency). The maximum kinetic energy and the stopping potential are Kmax and V0 respectively. If the frequency incident on the surface doubled, both the Kmax and V0 are also doubled. Statement-2 : The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light. (1) Statement-1 is true, Statement-2 is true; (2) Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-2 is not the correct explanation of Statement-1. Statement-1. (3) Statement-1 is false, Statement-2 is true. (4) Statement-1 is true, Statement-2 is false.

Q27.Energy required for the electron excitation in Li++ from the first to the third Bohr orbit is : (1) 36.3eV (2) 108.8eV (3) 122.4eV (4) 12.1eV

Q28.The half life of a radioactive substance is 20 minutes. The approximate time interval (t2 −t1) between the time t2 when 23 of it has decayed and time t1 and 31 of it had decayed is : (1) 14 min (2) 20 min (3) 28 min (4) 7 min

Q29.This question has Statement −1 and Statement −2. Of the four choices given after the statements, choose the one that best describes the two statements. Statement-1 : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals. Statement-2 : The state of ionosphere varies from hour to hour, day to day and season to season. (1) Statement-1 is true, Statement-2 is true; (2) Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-2 is not the correct explanation of Statement-1. Statement-1. (3) Statement- 1 is false, Statement- 2 is true. (4) Statement-1 is true, Statement-2 is false. JEE Main 2011 JEE Main Previous Year Paper

Q30.A screw gauge gives the following reading when used to measure the diameter of a wire. Main scale reading : 0 mm Circular scale reading : 52 divisions Given that 1 mm on main scale corresponds to 100 divisions of the circular scale. The diameter of wire from the above date is : (1) 0.052 cm (2) 0.026 cm (3) 0.005 cm (4) 0.52 cm

Q31.A 5.2 molal aqueous solution of methyl alcohol, CH3OH, is supplied. What is the mole fraction of methyl alcohol in the solution? (1) 0.190 (2) 0.086 (3) 0.050 (4) 0.100

Q32.The magnetic moment (spin only) of [NiCl4]2− is (1) 5.46BM (2) 2.83BM (3) 1.41BM (4) 1.82BM

Q33.A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emissions is at 680 nm, the other is at: (1) 325 nm (2) 743 nm (3) 518 nm (4) 1035 nm

Q34.Which one of the following order represents the correct sequence of the increasing basic nature of the given oxides ? (1) MgO < K2O < Al2O3 < Na2O (2) Na2O < K2O < MgO < Al2O3 (3) K2O < Na2O < Al2O3 < MgO (4) Al2O3 < MgO < Na2O < K2O

Q35.Which of the following statement is wrong? (1) Nitrogen cannot form dπ −pπ bond. (2) Single N −N bond is weaker than the single P −P bond, (3) N2O4 has two resonance structures (4) The stability of hydrides increases from NH3 to BiH3 in group 15 of the periodic table

Q36.Among the following the maximum covalent character is shown by the compound: (1) SnCl2 (2) AlCl3 (3) MgCl2 (4) FeCl2

Q37.The hybridization of orbitals of N atom in NO−3 , NO+2 and NH+4 are respectively : (1) sp2, sp, sp3 (2) sp, sp3, sp2 (3) sp2, sp3, sp (4) sp, sp2, sp3 Q38.'a' and 'b' are van der Waals' constants for gases. Chlorine is more easily liquefied than ethane because (1) a and b for Cl2 < a and b for C2H6 (2) a for Cl2 < a for C2H6 but b for Cl2 > b for C2H6 (3) a for Cl2 > a for C2H6 but b for Cl2 < b for (4) a and b for Cl2 > a and b for C2H6 C2H6 JEE Main 2011 JEE Main Previous Year Paper

Q39.The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of 10dm3 to a volume of 100dm3 at 27∘C is : (1) 35.8 J mol−1 K−1 (2) 32.3 J mol−1 K−1 (3) 42.3 J mol−1 K−1 (4) 38.3 J mol−1 K−1

Q40.A vessel at 1000 K contains CO2 with a pressure of 0.5 atm. Some of the CO2 is converted into CO on the addition of graphite. If the total pressure at equilibrium is 0.8 atm, the value of K is (1) 3 atm (2) 0.3 atm (3) 0.18 atm (4) 1.8 atm

Q41.Boron cannot form which one of the following anions? (1) BH−4 (2) B(OH)−4 (3) BO−2 (4) BF3−6

Q42.The strongest acid amongst the following compounds is : (1) HCOOH (2) CH3CH2CH(Cl)CO2H (3) ClCH2CH2CH2COOH (4) CH3COOH

Q43.Which of the following reagents may be used to distinguish between phenol and benzoic acid ? (1) Tollen's reagent (2) Molisch reagent (3) Neutral FeCl3 (4) Aqueous NaOH

Q44.Identify the compound that exhibits tautomerism. (1) Lactic acid (2) 2- Butene (3) Phenol (4) None of these

Q45.Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of : (1) a vinyl group (2) an isopropyl group (3) an acetylenic triple bond (4) two ethylenic double bonds

Q46.In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the face centre positions. If one atom of B is missing from one of the face centred points, the formula of the compound is (1) AB2 (2) A2B3 (3) A2 B5 (4) A2B

Q47.The degree of dissociation (α) of a weak electrolyte, AxBy is related to van't Hoff factor (i) by the expression: (1) α = x+y+1i−1 (2) α = x+y−1i−1 (3) α = x+y+1i−1 (4) α = (x+y−1)i−1

Q48.Ethylene glycol is used as an antifreeze in a cold climate. Mass of ethylene glycol which should be added to 4 kg of water to prevent it from freezing at −6∘C will be : [Kt for water = 1.86 K kg mol−1 , and molar mass of ethylene glycol = 62 g mol−1 ) (1) 204.30 g (2) 400.00 g (3) 304.60 g (4) 804.32 g JEE Main 2011 JEE Main Previous Year Paper

Q49.The reduction potential of hydrogen half cell will be negative if : (1) p (H2) = 1 atm and [H+] = 1.0M (2) p (H2) = 2 atm and [H+] = 1.0M (3) p (H2) = 2 atm and [H+] = 2.0M (4) p (H2) = 1 atm and [H+] = 2.0M