Solid States
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38. The percentage of empty space in a body centred cubic arrangement is ________.
(i) 74
(ii) 68
(iii) 32
(iv) 26
38. The percentage of empty space in a body centred cubic arrangement is ________.
(i) 74
(ii) 68
(iii) 32
(iv) 26
38. Option (iii) 32 is correct since the packing efficiency in bcc arrangement is 68%, therefore the percentage empty space can be calculated as – 100 - 68 = 32
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37. In which pair most efficient packing is present?
(i) Hcp and bcc
(ii) Hcp and ccp
(iii) Bcc and ccp
(iv) Bcc and simple cubic cell
37. In which pair most efficient packing is present?
(i) Hcp and bcc
(ii) Hcp and ccp
(iii) Bcc and ccp
(iv) Bcc and simple cubic cell
37. Option (ii) hcp and ccp is correct since in hcp and ccp the packing efficiency is 74% ( maximum ), hence this pair of packing is considered as the most efficient packing.
Upvote 22. Which of the following point defects are shown by AgBr(s) crystals?
(A) Schottky defect
(B) Frenkel defect
(C) Metal excess defect
(D) Metal deficiency defect
(i) (A) and (B)
(ii) (C) and (D)
(iii) (A) and (C)
(iv) (B) and (D)
22. Which of the following point defects are shown by AgBr(s) crystals?
(A) Schottky defect
(B) Frenkel defect
(C) Metal excess defect
(D) Metal deficiency defect
(i) (A) and (B)
(ii) (C) and (D)
(iii) (A) and (C)
(iv) (B) and (D)
36. Option (i) (A) and (B) is correct since AgBr shows both Frenkel as well as Schottky defects.
Upvote 21. The total number of tetrahedral voids in the face centred unit cell is __________.
(i) 6
(ii) 8
(iii) 10
(iv) 12
21. The total number of tetrahedral voids in the face centred unit cell is __________.
(i) 6
(ii) 8
(iii) 10
(iv) 12
35. Option (ii) 8 is correct since in face centred cubic unit cell the number of atoms per unit cell is 4 atoms and hence the number of tetrahedral voids in fcc unit cell is found to be 8
Upvote 34. To get a n-type semiconductor from silicon, it should be doped with a substance with valence__________.
(i) 2
(ii) 1
(iii) 3
(iv) 5
34. To get a n-type semiconductor from silicon, it should be doped with a substance with valence__________.
(i) 2
(ii) 1
(iii) 3
(iv) 5
34. Option (iv) 5 is correct since silicon is doped with a pentavalent substance like Phosphorus or Arsenic so, four out of five electrons are used in the formation of four covalent bonds with four of its neighbouring silicon atoms. The fifth electron is extra and becomes delocalised. These del
Upvote 33. Which of the following is true about the charge acquired by p-type semiconductors?
(i) Positive
(ii) Neutral
(iii) Negative
(iv) Depends on concentration of impurity
33. Which of the following is true about the charge acquired by p-type semiconductors?
(i) Positive
(ii) Neutral
(iii) Negative
(iv) Depends on concentration of impurity
33. Option (ii) neutral is correct since p-type semiconductor mainly contains positively charged carriers ( holes ) which are able to move freely. It is still considered to be neutral as the fixed acceptor atoms having accepted electrons are negative.
Upvote 32. Schottky defect is observed in crystals when __________.
(i) Some cations move from their lattice site to interstitial sites.
(ii) Equal number of cations and anions are missing from the lattice.
(iii) Some lattice sites are occupied by electrons.
(iv) Some impurity is present in the lattice.
32. Schottky defect is observed in crystals when __________.
(i) Some cations move from their lattice site to interstitial sites.
(ii) Equal number of cations and anions are missing from the lattice.
(iii) Some lattice sites are occupied by electrons.
(iv) Some impurity is present in the lattice.
32. Option (ii) equal number of cations and anions are missing from the lattice is correct since Schottky defect in crystals occurs when equal numbers of cations and anions are missing from the lattice.
Upvote 31. Cations are present in the interstitial sites in __________.
(i) Frenkel defect
(ii) Schottky defect
(iii) Vacancy defect
(iv) Metal deficiency defect
31. Cations are present in the interstitial sites in __________.
(i) Frenkel defect
(ii) Schottky defect
(iii) Vacancy defect
(iv) Metal deficiency defect
31. Option (i) Frenkel defect is correct since it is a type of defect in which an atom is dislocated from its lattice position to an interstitial site.
Upvote 30. Graphite cannot be classified as __________.
(i) Conducting solid
(ii) Network solid
(iii) Covalent solid
(iv) Ionic solid
30. Graphite cannot be classified as __________.
(i) Conducting solid
(ii) Network solid
(iii) Covalent solid
(iv) Ionic solid
30. Option (iv) ionic solid is correct since in graphite each atom is linked to the other through a covalent bond and hence it is a covalent solid and cannot fall under the category of ionic solid.
Upvote 29. The lattice site in a pure crystal cannot be occupied by _________.
(i) Molecule
(ii) Ion
(iii) Electron
(iv) Atom
29. The lattice site in a pure crystal cannot be occupied by _________.
(i) Molecule
(ii) Ion
(iii) Electron
(iv) Atom
29. Option (iii) electron is correct since lattice sites can only be occupied by electrons when there is imperfection in a solid and do not occur in pure crystals. Hence, the lattice site in a pure crystal cannot be occupied by electrons.
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