Actitud de los padres de los alumnos inmigrantes

12. An electron beam can undergo diffraction by crystals. Through what potential should a beam of electrons be accelerated so that its wavelength becomes equal to 1.54A. (1997) 13. A photon of wavelength 4000Å strikes a metal surface, the work function of metal being 2.13eV.

Calculate, the energy of Photon in eV, (ii) the kinetic energy of emitted photoelectron, and (iii) the velocity of photoelectron.

14. Following data were collected for the photoelectric emission of an electron from an element X, (in nm) KE(in eV)

254 1.93

313 0.9

365 0.5

405 0.2

λ

Calculate the wave function of an element X and also the value of Planck’s constant.

15. Iodine molecule dissociates into atoms after absorbing light to 4500A . If one quantum of radiation is absorbed by each molecule, calculate the kinetic energy of iodine atoms.

(Bond energy of I₂ = 240 kJ mol^–1) (1995)

16. In hydrogen atom, electrons are excited to 4th energy level. The number of lines that may appear in the spectrum will be

(a) 4 (b) 6 (c) 10 (d) 12

17. The velocity of an electron in the first Bohr orbit of a hydrogen atom is 6.32 × 10⁴ m/s. Its velocity in the second orbit would be

(a) 2.16 × 10⁴ (b) 1.5 × 10⁴ (c) 3.16 × 10⁴ (d) 3.16 × 10⁸

18. The electron energy in hydrogen atom is given by

12 2

21.7 10

E ergs

n

× −

= − . Calculate the energy

required to remove an electron completely from the n = 2 orbit. What is the longest wavelength (in cm) of light that can be used to cause this transition? (1984 ) 19. Estimate the difference in energy between 1st and 2nd Bohr’s orbit for a hydrogen atom. At what

minimum atomic number, a transition from n = 2 to n = 1 energy level would result in the emission of X-rays with _{λ =3.0 10×} ⁻⁸_m? Which hydrogen atom-like species does this atomic number

corre-spond to? (1993)

20. Calculate the wavelength in Angstroms of the photon that is emitted when an electron in the Bohr’s

21. An electron in a hydrogen atom absorbs 1.5 times as much energy as the minimum required for its escape (i.e., 13.6 eV) from the atom. Calculate the wavelength of the emitted electron.

22. Calculate the Bohr radius of third orbit of He⁺ ion.

23. What is the velocity of electron in Bohr’s second orbit of H-atom?

24. Calculate the wave number of the shortest wavelength transition in Balmer series of atomic hydrogen.

25. Electromagnetic radiations of wavelength 242 nm is just sufficient to ionize sodium atom. Calculate the ionization energy of sodium in kJ/mol.

26. The energy of the electron in the second and third Bohr orbits of the hydrogen atom is –5.42 × 10^–12 ergs and –2.41 × 10^–12 ergs respectively. Calculate the wavelength of the emitted radiation, when the electron drops from third to second orbit.

27. Calculate the frequency of the spectral line emitted when the electron in n = 3 in hydrogen atom is de-excited to the ground state (Rydberg constant = 109, 737 cm^-1).

28. Find the number of waves made by a Bohr electron in one complete revolution in its third orbit.

29. The ionization potential of hydrogen atom is 13.6 eV. The energy required to remove an electron from n = 2 state of the hydrogen atom is

(a) 3.4 eV (b) 6.8 eV (c) 13.6 eV (d) 27.2 eV

30. If the wavelength of the first line of the Balmer series of hydrogen atom is 656.1 nm, the wavelength of the second line of this series would be

(a) 218.7 nm (b) 328.0 nm

(c) 486.0 nm (d) 640.0 nm

31. The ratio of kinetic energy and potential energy of an electron in a Bohr orbit of a hydrogen-like species is

(a) 1

2 (b) 1

−2 (c) 1 (d) –1

32. The ratio of kinetic energy and total energy of an electron in a Bohr orbit of a hydrogen-like species is

(a) 1

2 (b) (c) 1 (d) –1

33. The ratio of potential energy and total energy of an electron in a Bohr orbit of a hydrogen-like species is

(a) 2 (b) –2 (c) 1 (d) –1

34. What is the wavelength emitted during the transition of electron in between two levels of He⁺ ion whose sum is 5 and difference is 3?

(a) 200 A° (b) 250 A°

(c) 244 A° (d) 240 A°

35. Consider the hydrogen atom to be a proton embedded in a cavity of radius a₀ (Bohr’s radius) whose charge is neutralized by the addition of an electron to the cavity in vacuum, infinitely slowly. Esti-mate the average total energy of an electron in its ground state in a hydrogen atom as the work done in the above neutralisation process. Also, if the magnitude of the average kinetic energy is half the magnitude of the average potential energy, find the average potential energy. (1996)

*36. 1.8 g of hydrogen atoms are excited by the radiations. The study of spectra indicates that 27% of the atoms are in third energy level and 15% of atoms in second energy level and rest in ground state.

Ionization energy of H atom is 13.6 eV. Calculate

(i) the number of atoms present in third and second energy levels, (ii) the total energy evolved when all the atoms returned to ground state.

*37. The ionization energy of H is 13.6 eV, it is exposed to electromagnetic waves of wavelength 1028Å and gives out induced radiations. Find the wavelength of these induced radiations.

38. The angular momentum of an electron in a Bohr’s orbit of H-atom is 4.2178 × 10^–34 kg m²/s.

Calculate the spectral line emitted when electron falls from this level to next lower level.

39. Which electronic level allows the hydrogen atom to absorb a photon but not emit photon?

(a) 3s (b) 1s

(c) 2p (d) 3d

*40. The temperature at which the de Broglie wavelength of helium atom is 0.62 A° will be (Atomic mass of helium = 4.04)

(a) 710.5 K (b) 750.4 K

(c) 410.75 K (d) 570.4 K

41. A dust particle has mass equal to 10^–11 g, diameter of 10^–4 cm and velocity 10^–4 cm s^–1. The error in measurement of velocity is 0.1^–1. Calculate the uncertainty in its position. Comment on the result.

42. What is the maximum precision with which the momentum of an electron may be known if the position is determined within ± 0.0001Å.

43. (a) The Schrodinger wave equation for hydrogen atom is:

( )

44. The principal quantum number of an atom is related to the : (1983) (a) size of the orbital (b) spin angular momentum

(c) orientation of the orbital in space (d) orbital angular momentum

45. The electrons, identified by quantum numbers n and l

(i) n = 5, l = 1 (ii) n = 5, l = 0 (iii) n = 4, l = 1 (iv) n = 4, l = 2, can be placed in order of increasing energy, from the lowest to highest, as

(a) (ii) < (iii) < (iv) < (i) (b) (iii) < (ii) < (iv) < (i) (c) (i) > (iv) > (ii) > (iii) (d) (i) > (iv) > (iii) > (ii) 46. Which of the following sets of quantum numbers is not allowed?

(a) n = 3, l = 1, m = +2 (b) n = 3, l = 1, m = +1 (c) n = 3, l = 0, m = 0 (d) n = 3, l = 2, m ± 2 47. Which of the following sets of quantum number is/are not allowed.

(I) n = 4, l = 3, m = - 1, s = + 1

2 (II) n = 2, l = 3, m = + 1, s = - 1 2 (III) n = 3, l = 0, m = + 1, s = + 1

2 (IV) n = 2, l = 2, m = + 1, s = + 1 2 (a) only I (b) II, III and IV (c) only II and III (d) only IV

48. Correct set of four quantum numbers for the valence (outermost) electron of rubidium (Z = 37) is : (1984) (a) 5, 0, 0, 1

+2 (b) 5, 1, 0, 1

+2 (c) 5, 1, 1, 1

+2 (d) 6, 0, 0, 1 +2

49. Which of the following atoms would be expected to be most paramagnetic?

(a) 3^Li (b) 4^Be

(c) 5^B (d) 6^C

50. The ratio of magnetic moments of Cr, Cu, Fe is

(a) 4 : 1: 8 (b) _{6 : 1: 4}

(c) 2 : 1: 8 (d) 8 : 1: 8

51. A _3d orbital has

(a) zero radial and two angular nodes (b) two radial and two angular nodes.

(c) three radial and three angular nodes (d) two radial and zero angular nodes

52. Ground state electronic configuration of oxygen atom can be represented by

(a) (b)

(c) (d)

53. Give reason why the ground state outermost electronic configuration of silicon is : (1985)

and no t

3s 3p 3s 3p

54. Which of the following statement(s) is(are) correct?

(a) Oxygen molecule is diamagnetic

(b) The electronic configuration of Au is 5d¹⁰6s¹

(c) In silver atom, 23 electrons have a spin of one type and 24 of the opposite type (d) The oxidation state of nitrogen is N₃H is –3

55. What is the maximum number of electrons that may be present in all the atomic orbitals with principal quantum number 3 and the azimuthal quantum number 2? (1985) 56. A compound of vanadium has a magnetic moment of 1.73 BM. Work out the electronic

configuration of the vanadium ion in the compound. (1997) 57. Write electonic configuration of the following: C(z = 6), Ar(z = 18), Br(z = 35), Cs (z = 55)

58. Write electronic configuration of Mn²⁺ ion and calculate (i) number of unpaired electrons, (ii) magnetic moment and find whether the ion is paramagnetic or diamagnetic.

(a) Statement– I is True, Statement–II is True;

Statement– II is a correct explanation for Statement– I (b) Statement– I is True, Statement– II is True;

Statement–II is not a correct explanation for Statement– I (c) Statement–I is True, Statement–II is False

(d) Statement– I is False, Statement–II is True.

59. Statement 1: - An orbital cannot have more than two electrons

Statement 2:- The two electrons in an orbital create opposing magnetic field.

60. Statement 1:- On increasing the intensity of radiation, the number of photoelectrons ejected and their KE increases.

Statement 2:- Greater intensity means, greater energy which in turn means greater frequency of radiation

62. Statement 1:- Angular momentum of e^– in 1s, 2s, 3s etc. is zero Statement 2:- 1s, 2s 3s ... all have spherical shape

63. Statement 1:- In Rutherford’s gold foil experiment, very few _α-particles are deflected back.

Statement 2:- Nucleus present inside the atom is heavy.

64. Statement–I : Band gap in germanium is small.

Because

Statement–II: The energy spread of each germanium atomic energy level is infinitesimally small.

(2007) 65. Match the following

Column I Column II

(i) Aufbau principle P. Line spectrum invisible region (ii) de Broglie Q. Orientation of e^– in an orbital

(iii) Hund’s rule R. _{λ = = νh m}

(iv) Balmer series S. Electronic configuration

66. Column I Column II

(i) Thomson P. Exclusion principle

(ii) Pauli Q. Atomic model

(iii) Bohr R. Cathode rays

(iv) Chadwick S. Neutron

67. Column I Column II

(i) Cathode rays P. Helium nuclei

(ii) Alpha particles Q. Dumbell

(iii) X-rays R. electrons

(iv) P-orbitals S. Electro magnetic radiation

68. According to Bohr’s theory E_n = total energy

K_n = Kinetic energy V_n = Potential energy

r_n = Radius of nth orbit (2006)

Match the following:

Column I Column II

(A) V_n / K_n = ? (P) 0

(B) If radius of nth oribit ∝E_n^x, x=? (Q) –1 (C) Angular momentum in lowest orbital (R) –2

(D) ^y, ?

n

1 z y

r ∝ = (S) 1

Passage

Based upon the information given below, answer the questions that follow:

According to Bohr’s theory for single electron species. The radius of orbit of an e^–

2 n

r 0.52 9 n Å

= × Z ,

the velocity of e^– in an orbit, _n ⁶ z 2.18 10 m / s

ν = × ×n and, the Energy of e^– in an orbit

2

n 2

E 13.6 Z eV / atom

= − ×n .

Where n is the orbit in which e^– revolves and Z is the atomic number of species

69. The radius of second orbit of He⁺ ion is:

(a) 0.529 Å (b) 0.529 × 2 Å (c) 0.529 × 4 Å (d) 0.529 × 1

2 Å

70. The ratio of velocities of electron in third orbit of H-atom to that of electron in second orbit of Li²⁺ ion is:

(a) 1

2 (b) 3

2 (c) 2

9 (d) 1

3 71. The energy required to remove an electron from 1st excited state of H-atom is:

(a) + 13.6 eV (b) + 3.4 eV (c) + 1,9 eV (d) zero

In document UNIVERSIDAD COMPLUTENSE DE MADRID (página 74-81)