Solid State-NCERT Exemplar Problems & Solution
MCQs-II
31. Which of the following is not true about the ionic solids?
(i) Bigger ions form the close packed structure.
(ii) Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size.
(iii) Occupation of all the voids is not necessary.
(iv) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.
Answer: (iv) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.
32. A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field becuase ________.
(i) all the domains get oriented in the direction of magnetic field.
(ii) all the domains get oriented in the direction opposite to the direction of magnetic field.
(iii) domains get oriented randomly.
(iv) domains are not affected by magnetic field.
Answer: (i) all the domains get oriented in the direction of magnetic field.
33. The correct order of the packing efficiency in different types of unit cells is ________.
(i) fcc < bcc < simple cubic
(ii) fcc > bcc > simple cubic
(iii) fcc < bcc > simple cubic
(iv) bcc < fcc > simple cubic
Answer: (ii) fcc > bcc > simple cubic
34. Which of the following defects is also known as dislocation defect?
(i) Frenkel defect
(ii) Schottky defect
(iii) Non-stoichiometric defect
(iv) Simple interstitial defect
Answer: (i) Frenkel defect
35. In the cubic close packing, the unit cell has ________.
(i) 4 tetrahedral voids each of which is shared by four adjacent unit cells.
(ii) 4 tetrahedral voids within the unit cell.
(iii) 8 tetrahedral voids each of the which is shared by four adjacent unit cells.
(iv) 8 tetrahedral voids within the unit cells.
Answer: (iv) 8 tetrahedral voids within the unit cells.
36. The edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc and simple cubic unit cell are respectively________.
(i) `2sqrt(2r), (4r)/sqrt3, 2r`
(ii) `(4r)/sqrt3, 2sqrt(2r), 2r`
(iii) `2r, 2sqrt(2r), (4r)/sqrt3`
(iv) `2r, (4r)/sqrt3, 2sqrt(2r)`
Answer: (i) `2sqrt(2r), (4r)/sqrt3, 2r`
37. Which of the following represents correct order of conductivity in solids?
(i) Kmetals >> Kinsulators < Ksemiconductors
(ii) Kmetals << Kinsulators < Ksemiconductors
(iii) Kmetals
(iv) Kmetals>Ksemiconductors > Kinsulator `!=`zero
Answer: (i) Kmetals >> Kinsulators < Ksemiconductors
II. Multiple Choice Questions (Type-II)
Note : In the following questions two or more options may be correct.
38. Which of the following is not true about the voids formed in 3 dimensional hexagonal close packed structure?
(i) A tetrahedral void is formed when a sphere of the second layer is present above triangular void in the first layer.
(ii) All the triangular voids are not covered by the spheres of the second layer.
(iii) Tetrahedral voids are formed when the triangular voids in the second layer lie above the triangular voids in the first layer and the triangular shapes of these voids do not overlap.
(iv) Octahedral voids are formed when the triangular voids in the second layer exactly overlap with similar voids in the first layer.
Answer: (iii) Tetrahedral voids are formed when the triangular voids in the second layer lie above the triangular voids in
And
(iv) Octahedral voids are formed when the triangular voids in the second layer exactly overlap with similar voids in the first layer.
39. The value of magnetic moment is zero in the case of antiferromagnetic substances because the domains ________.
(i) get oriented in the direction of the applied magnetic field.
(ii) get oriented opposite to the direction of the applied magnetic field.
(iii) are oppositely oriented with respect to each other without the application of magnetic field.
(iv) cancel out each other’s magnetic moment.
Answer: (iii) are oppositely oriented with respect to each other without the application of magnetic field.
And
(iv) cancel out each other’s magnetic moment.
40. Which of the following statements are not true?
(i) Vacancy defect results in a decrease in the density of the substance.
(ii) Interstitial defects results in an increase in the density of the substance.
(iii) Impurity defect has no effect on the density of the substance.
(iv) Frankel defect results in an increase in the density of the substance.
Answer:
(iii) Impurity defect has no effect on the density of the substance.
And
(iv) Frankel defect results in an increase in the density of the substance.
41. Which of the following statements are true about metals?
(i) Valence band overlaps with conduction band.
(ii) The gap between valence band and conduction band is negligible.
(iii) The gap between valence band and conduction band cannot be determined.
(iv) Valence band may remain partially filled.
Answer:
(i) Valence band overlaps with conduction band.
(ii) The gap between valence band and conduction band is negligible.
And
(iv) Valence band may remain partially filled.
42. Under the influence of electric field, which of the following statements is true about the movement of electrons and holes in a p-type semi conductor?
(i) Electron will move towards the positvely charged plate through electron holes.
(ii) Holes will appear to be moving towards the negatively charged plate.
(iii) Both electrons and holes appear to move towards the positively charged plate.
(iv) Movement of electrons is not related to the movement of holes.
Answer:
(i) Electron will move towards the positvely charged plate through electron holes.
And
(ii) Holes will appear to be moving towards the negatively charged plate.
43. Which of the following statements are true about semiconductors?
(i) Silicon doped with electron rich impurity is a p-type semiconductor.
(ii) Silicon doped with an electron rich impurity is an n-type semiconductor.
(iii) Delocalised electrons increase the conductivity of doped silicon.
(iv) An electron vacancy increases the conductivity of n-type semiconductor.
Answer:
(ii) Silicon doped with an electron rich impurity is an n-type semiconductor.
And
(iii) Delocalised electrons increase the conductivity of doped silicon.
Explanation
Conductivity of n– type semiconductor is due to presence of free electron delocalization of electrons increases the conductivity of doped silicon deu to increase in mobility of electron.
44. An excess of potassium ions makes KCl crystals appear violet or lilac in colour since ________.
(i) some of the anionic sites are occupied by an unpaired electron.
(ii) some of the anionic sites are occupied by a pair of electrons.
(iii) there are vacancies at some anionic sites.
(iv) F-centres are created which impart colour to the crystals.
Answer:
(i) some of the anionic sites are occupied by an unpaired electron.
And
(iv) F-centres are created which impart colour to the crystals.
45. The number of tetrahedral voids per unit cell in NaCl crystal is ________.
(i) 4
(ii) 8
(iii) twice the number of octahedral voids.
(iv) four times the number of octahedral voids.
Answer:
(ii) 8
And
(iii) twice the number of octahedral voids.
46. Amorphous solid can also be called ________.
(i) pseudo solids
(ii) true solids
(iii) super cooled liquids
(iv) super cooled solids
Answer:
(i) pseudo solids
And
(iii) super cooled liquids
47. A perfect crystal of silicon (Fig) is doped with some elements as given in the options. Which of these options show n-type semiconductors?
(i) 
(ii) 
(iii) 
(iv) 
Answer:
(i)
And
(iii)
48. Which of the following statements are correct?
(i) Ferrimagnetic substances lose ferrimagnetism on heating and become paramagnetic.
(ii) Ferrimagnetic substances do not lose ferrimagnetism on heating and remain ferrimagnetic.
(iii) Antiferromagnetic substances have domain structures similar to ferromagnetic substances and their magnetic moments are not cancelled by each other.
(iv) In ferromagnetic substances all the domains get oriented in the direction of magnetic field and remain as such even after removing magnetic field.
Answer:
(i) Ferrimagnetic substances lose ferrimagnetism on heating and become paramagnetic.
And
(iv) In ferromagnetic substances all the domains get oriented in the direction of magnetic field and remain as such even after removing magnetic field.
49. Which of the following features are not shown by quartz glass?
(i) This is a crystalline solid.
(ii) Refractive index is same in all the directions.
(iii) This has definite heat of fusion.
(iv) This is also called super cooled liquid.
Answer:
(i) This is a crystalline solid.
And
(iii) This has definite heat of fusion.
Explanation:
Quartz glass is an amorphous solid so it has not definite heat of fusion. This is due to short range order of molecule while quartz glass is also known as super cooled liquid and isotriopic in nature.
50. Which of the following cannot be regarded as molecular solid?
(i) SiC (Silicon carbide)
(ii) AlN
(iii) Diamond
(iv) `I_2`
Answer:
(i) SiC (Silicon carbide)
(ii) AlN
And
(iii) Diamond
51. In which of the following arrangements octahedral voids are formed?
(i) hcp
(ii) bcc
(iii) simple cubic
(iv) fcc
Answer:
(i) hcp
And
(iv) fcc
52. Frenkel defect is also known as ________.
(i) stoichiometric defect
(ii) dislocation defect
(iii) impurity defect
(iv) non-stoichometric defect
Answer:
(i) stoichiometric defect
And
(ii) dislocation defect
53. Which of the following defects decrease the density?
(i) Interstitial defect
(ii) Vacancy defect
(iii) Frankel defect
(iv) Schottky defect
Answer:
(ii) Vacancy defect
And
(iv) Schottky defect
Reference:
Questions are taken from NCERT Book: Exemplar Problems