Question with Answer JEE Mains
1. The binding energy per nucleon for the parent nucleus is E1 and that for the daughter nuclei is E2. Then
(a) E2 = 2E1
(b) E1 > E2
(b) E1 > E2
(c) E2 > E1
(d) E1 = 2E2
(d) E1 = 2E2
Ans. c
2. A diatomic ideal gas is used in a car engine as the working substance. If during the adiabatic expansion part of the cycle, volume of the gas increases from V to 32 V, the efficiency of the engine is
5. Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 30° with each other. When suspended in a liquid of density 0.8 g cm–3, the angle remains tho same. If density of the material of the sphere is 16 g cm–3, the dielectric constant of the liquid is
2. A diatomic ideal gas is used in a car engine as the working substance. If during the adiabatic expansion part of the cycle, volume of the gas increases from V to 32 V, the efficiency of the engine is
(a) 0.5
(b) 0.75
(b) 0.75
(c) 0.99
(d) 0.25
(d) 0.25
Ans. b
3. If a source ol power 4 kW produces 1020 photons/second, the radiation belong to a part of the spectrum called
(a) X-rays
(b) ultraviolet rays
(b) ultraviolet rays
(c) microwaves
(d) y-rays
(d) y-rays
Ans. a
4. The respective number of significant figures for the numbers 23.023, 0.0003 & 2.1 × 10–3 are
(a) 5, 1, 2
(b) 5, 1, 5
(b) 5, 1, 5
(c) 5, 5, 2
(d) 4, 4, 2
(d) 4, 4, 2
Ans. a
5. Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 30° with each other. When suspended in a liquid of density 0.8 g cm–3, the angle remains tho same. If density of the material of the sphere is 16 g cm–3, the dielectric constant of the liquid is
(a) 4
(b) 3
(b) 3
(c) 2
(d) 1
(d) 1
Ans. c
6. As the beam enters the medium, it will
7. The initial shape of the wavefront of the beam is
6. As the beam enters the medium, it will
(a) diverge
(b) converge
(c) diverge near the axis and converge near the periphery
(d) travel as a cylindrical beam
Ans. b
7. The initial shape of the wavefront of the beam is
(a) convex
(b) concave
(c) convex near the axis and concave near the periphery
(d) planar
Ans. d
8. The speed of light in the medium is
(a) minimum on the axis of the beam
(b) the same everywhere in the beam
(c) directly proportional to the intensity l
(d) maximum on the axis of the beam
Ans. a
9. The standard enthalpy of formation of NH3 is –46.0 kJ mol–1 If the enthalpy of formation of H2 from its atoms is –436 kJ mol–1 and that of N2 is –712 kJ mol–1, the average bond enthalpy of N—H bond in NH3 is
9. The standard enthalpy of formation of NH3 is –46.0 kJ mol–1 If the enthalpy of formation of H2 from its atoms is –436 kJ mol–1 and that of N2 is –712 kJ mol–1, the average bond enthalpy of N—H bond in NH3 is
(a) –964 kJ mol–1
(b) +352 kJ mol–1
(b) +352 kJ mol–1
(c) +1056 kJ mol–1
(d) –1102 kJ mol–1
(d) –1102 kJ mol–1
Ans. b
10. The time for half-life period of a certain reaction, A → products is 1 h. When the initial concentration of the reactant 'A', is
10. The time for half-life period of a certain reaction, A → products is 1 h. When the initial concentration of the reactant 'A', is
2.0 mol L–1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L–1, if it is a zero order reaction?
(a) 4 h
(b) 0.5 h
(b) 0.5 h
(c) 0.25 h
(d) 1 h
(d) 1 h