Practice Questions

Q70.If 13.6eV energy is required to ionize the hydrogen atom, then the energy required to remove an electron from n = 2 is (1) 10.2eV (2) 0eV (3) 3.4eV (4) 6.8eV

Q71.At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit (i) electrons (ii) protons (iii) He2+ (iv) neutrons The emission at instant can be (1) i, ii, iii (2) i, ii, iii, iv (3) iv (4) ii, iii

Q72.If N0 is the original mass of the substance of half- life period t1/2 = 5 years, then the amount of substance left after 15 years is (1) N0/8 (2) N0/16 (3) N0/2 (4) N0/4

Q73.If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should (1) increase (2) remain unchanged (3) decrease (4) first increase then decrease

Q74.At absolute zero, Si acts as (1) non metal (2) metal (3) insulator (4) none of these

Q75.The energy band gap is maximum in (1) metals (2) superconductors (3) insulators (4) semiconductors

Q76.The part of a transistor which is most heavily doped to produce large number of majority carriers is (1) emmiter (2) base (3) collector (4) can be any of the above three

Q77.In a compound C, H and N atoms are present in 9 : 1 : 35 by weight. Molecular weight of compound is 108. Molecular formula of compound is (1) C2H6N2 (2) C3H4N (3) C6H8N2 (4) C9H12N3

Q78.Number of atoms in 558.5 gram Fe (at.wt. of Fe = 55.85 g mol−1 ) is (1) twice that in 60 g carbon (2) 6.023 × 1022 (3) half that in 8g He (4) 558.5 × 6.023 × 1023

Q79.In a hydrogen atom, if energy of an electron in ground state is 13.6 eV, then that in the 2nd excited state is JEE Main 2002 JEE Main Previous Year Paper (1) 1.51 eV (2) 3.4 eV (3) 6.04 eV (4) 13.6 eV

Q80.Uncertainity in position of a minute particle of mass 25 g in space is 10−5 m. What is the uncertainity in its velocity (in ms−1)? ( h = 6.6 × 10−34Js) (1) 2.1 × 10−34 (2) 0.5 × 10−34 (3) 2.1 × 10−28 (4) 0.5 × 10−23 Q81. β - particle is emitted in radioactivity by (1) conversion of proton to neutron (2) from outermost orbit (3) conversion of neutron to proton (4) β-particle is not emitted

Q82.In which of the folloiwng species the interatomic bond angle is 109∘28′? (1) NH3, (BF4)−1 (2) (NH4)+, BF3 (3) NH3, BF4 (4) (NH2)−1, BF3

Q83.Which of the following are arranged in an increasing order of their bond strengths ? (1) O−2 < O2 < O+2 < O2−2 (2) O2−2 < O−2 < O2 < O+2 (3) O−2 < O2−2 < O2 < O+2 (4) O+2 < O2 < O−2 < O2−2

Q84.Which of the following statements is true ? (1) HF is less polar than HBr (2) absolutely pure water does not contain any ions (3) chemical bond formation take place when forces (4) in covalency transference of electron takes place of attraction overcome the forces of repulsion

Q85.For an ideal gas, number of moles per litre in terms of its pressure P, gas contant R and temperature T is (1) PT/R (2) PRT (3) P/RT (4) RT/P

Q86.Value of gas constant R is (1) 0.082 litre atm (2) 0.987cal mol−1 K−1 (3) 8.3 J mol−1 K−1 (4) 83 erg mol−1 K−1

Q87.Kinetic theory of gases proves (1) only Boyle’s law (2) only Charles’ law (3) only Avogadro’s law (4) all of these

Q88.If an endothermic reaction is non- spantaneous at freezing point of water and becomes feasible at its boiling point, then (1) ΔH is - ve, ΔS is + ve (2) ΔH and ΔS both are + ve (3) ΔH and ΔS both are − ve (4) ΔH is + ve, ΔS is −ve

Q89.A heat engine absorbs heat Q1 at temperature T1 and heat Q2 at temperature T2 . Work done by the engine is J (Q1 + Q2). This data (1) violates 1st law of thermodynamics (2) violates 1st law of thermodynamics if Q1 is −ve (3) violates 1st law of thermodynamics if Q2 is − ve(4) does not violate 1st law of thermodynamics

Q90.The heat required to raise the temperature of body by 1 K is called JEE Main 2002 JEE Main Previous Year Paper (1) specific heat (2) thermal capacity (3) water equivalent (4) none of these

Q91.Change in volume of the system does not alter the number of moles in which of the following equilibria ? (1) N2( g) + O2( g) ⇌2NO(g) (2) PCl5( g) ⇌PCl3( g) + Cl2( g) (3) N2( g) + 3H2( g) ⇌2NH3( g) (4) SO2Cl2( g) ⇌SO2( g) + Cl2( g)

Q92.In which of the following reactions, increase in the volume at constant temperature does not affect the number of moles at equilibrium (1) 2NH3 →N2 + 3H2 (2) C(g) + (1/2)O2( g) →CO(g) (3) H2( g) + O2( g) →H2O2( g) (4) none of these

Q93.For the reaction CO(g) + (1/2)O2( g) = CO2( g), Kp/Kc is (1) RT (2) (RT)−1 (3) (RT)−1/2 (4) (RT)1/2 Q94.1 M NaCl and 1 M HCl are present in an aqueous solution. The solution is (1) not a buffer solution with pH < 7 (2) not a buffer solution with pH > 7 (3) a buffer solution with pH < 7 (4) a buffer solution with pH > 7

Q95.Species acting as both Bronsted acid and base is (1) (HSO4)−1 (2) Na2CO3 (3) NH3 (4) OH−1

Q96.Let the solubility of an aqueous solution of Mg(OH)2 be x then its ksp is (1) 4x3 (2) 108x5 (3) 27x4 (4) 9x