1. A mineral having the formula AB2 crystallizes in the c.c.p. lattice, with A atoms occupying the lattice points. The CN of A is 8 and that of B is 4. What percentage of the tetrahedral sites is occupied by B atoms?
(1) 25% (2) 50%
(3) 75% (4) 100%
2. CsBr has b.c.c. structure with edge length 4.3. The shortest inter ionic distance in between Cs+ and Br– is
(1) 3.72 (2) 1.86
(3) 7.44 (4) 4.3
3. The formula for determination of density of cubic unit cell is
(1) 0 3
4. The closest-packing sequence ABAB ... represents
(1) Primitive cubic packing (2) Body-centred cubic packing (3) Face-centred cubic packing (4) hexagonal packing
5. In Bragg’s equation for diffraction of X-rays ‘n’ represents
(1) The number of mole (2) Quantum number
(3) The order of reflection (4) Avogadro’s number 6. Tetragonal crystal system has the following unit cell dimensions
(1) a = b = c and α=β=γ=90° (2) a=b≠candα=β=γ=90° (3) a≠b≠candα=β=γ=90° (4) a=b≠candα=β=90°,γ=120°
7. In a solid lattice, the cation has left a lattice site and is located at interstitial position, the lattice defect is
(1) Interstitial defect (2) Vacancy defect
(3) Frenkel defect (4) Schottky defect
8. Each unit cell of NaCl consists of 13 chloride ions and _______.
(1) 13 Na+ ions (2) 14 Na+ ions
(3) 6 Na+ ions (4) 8 Na+ ions
9. Germanium or silicon becomes semi-conductor due to (1) Schottky defect
(2) Chemical impurity (3) Frenkel defect (4) None of these
10. Which one of the following is correct?
(1) Schottky defect lowers the density
(2) Frenkel defect increases the dielectric constant of the crystals (3) Stoichiometric defects make the crystals good electrical conductors (4) All of these
11. The electrons trapped in anion vacancies in metal excess defects are called
(1) Mobile electrons (2) Trapped electrons
(3) Valence electrons (4) F-centres
12. The correct statement regarding F-centre is (1) Electrons are held in the voids of crystals (2) F-centre provides colour to the crystals
(3) Conductivity of the crystal increases due to F-centre (4) All of these
13. Crystals where dipoles may align themselves in an ordered manner, so that there is a net dipole moment, exhibit
(1) Pyro-electricity (2) Piezo-electricity
(3) Ferro-electricity (4) Anitferro electricity
14. Some of the polar crystals, on heating produce a small electric current called
(1) Pyro-electricity (2) Piezo-electricity
(3) Ferro-electricity (4) Anitferro-electricity
15. Germanium is an example of
(1) An intrinsic semiconductor (2) An n-type semiconductor
(3) A p-type semiconductor (4) Insulator
16. Which type of semiconductor is obtained on mixing the arsenic into the silicon?
(1) n-type (2) p-type
(3) Internal (4) both (1) and (2)
17. If indium is added in small quantity of Ge metal, we get
(1) An n-type semiconductor (2) A p-type semiconductor
(3) Rectifier (4) Insulator
18. When n- and p-type semiconductors are allowed to come into contact
(1) Some electrons will flow from n to p (2) Some electrons will flow from p to n (3) The impurity element will flow from n to p (4) The impurity element will flow from p to n 19. The electrical conductivity of semiconductors
(1) Increases with temperature (2) Decreases with temperature (3) Remains constants on heating (4) None of the above
20. Super conductors are substances which
(1) Conduct electricity at low temperature (2) Conduct electricity at high temperatures (3) Offer high resistance to the flow of current (4) Offer no resistance to the flow of current
21. The phenomenon of superconductivity was first discovered by
(1) Einstein (2) Soddy
(3) Hund and Mulliken (4) Kammerlingh Onnes
22. Which substances possess zero resistance at 0 K?
(1) Conductors (2) Semiconductors
(3) Superconductors (4) Insulators
23. Amorphous solids are
(1) Solid substances in real sense (2) Liquids in real sense
(3) Supercooled liquids (4) Substances with definite M.P.
24. Which of the following is not an example of molecular crystal?
(1) Hydrogen (2) Iodine
(3) Ice (4) Sodium chloride
25. The pure crystalline substance on being heated gradually first forms a turbid liquid at constant temperature and still at higher temperature turbidity completely disappears. The behaviour is a characteristic of substance forming
(1) Allotropic crystals (2) Liquid crystals
(3) Isomeric crystals (4) Isomorphous crystals
26. The co-ordination number of a body-centred atom in cubic structure is
(1) 4 (2) 6
(3) 8 (4) 12
27. The radius of an ion in a body centred cube of edge a is (1) 2
a (2) 2
4 a
(3) 3 4
a (4) a
28. The fraction of the total volume occupied by atoms in a simple cube is (1) 2
π (2)
8 3π
(3) 6
2π
(4) 6 π
29. A substance AxBy crystallizes in an f.c.c. lattice in which atoms of ‘A’ occupy each corner of the cube and atoms of ‘B’ occupy the centres of each face of the cube. Identify the correct composition of the substance AxBy.
(1) AB3 (2) A4B3
(3) A3B (4) Composition cannot be specified
30. In a closed packed lattice, the number of octahedral sites as compared to tetrahedral ones will be
(1) Equal (2) Half
(3) Double (4) None of these
31. CsCl on heating to 760 K changes into
(1) Liquid (2) NaCl structure
(3) ZnS structure (4) None of these
32. Compounds having NaCl type structure when subjected to high pressure changes into
(1) Unstable compound (2) CsCl type structure
(3) ZnS type structure (4) None of the three
33. In a face centred cubic cell, an atom at the face centre is shared by
(1) 4 unit cells (2) 2 unit cells
(3) 1 unit cell (4) 6 unit cells
34. Ionic solids are characterised by
(1) Good conductivity in solid state (2) High vapour pressure (3) Low melting point (4) Solubility in polar solvents 35. Silicon is a
(1) Conductor (2) Semiconductor
(3) Non conductor (4) Metal complex
36. On adding a little phosphorus to silicon, we get a/an
(1) n-Type semiconductor (2) p-Type semiconductor
(3) Metallic conductor (4) Insulator
37. Piezoelectric crystals are used in
(1) Radio (2) TV
(3) Record player (4) Refrizerator
38. Glass is
(1) Supercooled liquid (2) Crystalline solid
(3) Liquid crystal (4) None of these
39. In a crystal pair of ions are missing from normal sites. This is an example of
(1) F-centres (2) Interstitial defect
(3) Frenkel defect (4) Schottky defect
40. Frenkel defect generally appears in
(1) AgBr (2) ZnS
(3) AgI (4) All of these
41. Missing of one cation and one anion from the crystal lattice is called :
(1) Ionic defect (2) Crystal defect
(3) Schottky defect (4) Frenkel defect
42. In a closed packed array of N spheres, the number of tetrahedral holes are
(1) N/2 (2) N
(3) 4N (4) 2N
43. For an ionic crystal of general formula AX and co-ordination number 6, the value of radius ratio will be
(1) Greater than 0.73 (2) In between 0.732 and 0.414
(3) In between 0.41 and 0.22 (4) Less than 0.22
44. Close packing is maximum in the crystal lattice of:
(1) Face-centred cubic (2) Body-centred cubic
(3) Simple-centred cubic (4) None of these
45. In the crystal of CsCl, the nearest neighbours of each Cs ion are
(1) Six chloride ions (2) Eight Cs ions
(3) Six Cs ions (4) Eight chloride ions
46. Schottky defect in crystals is observed when
(1) An ion leaves its normal site and occupies an interstitial site (2) Equal number of cations and anions are missing from the lattice (3) Unequal number of cations and on ions are missing from the lattice (4) Density of the crystal is increased
47. Pick up the correct statement
(1) The ionic crystal of AgBr does not have Schottky defect
(2) The unit cell having crystal parameters, a=b≠c, α=β= 90°, γ=120° is hexagonal (3) In ionic compounds having Frenkel defect, the ratio r+/r– is high
(4) The coordination number of Na+ ion in NaCl is 4
48. When NaCl is dopped with MgCl2 the nature of defect produced is
(1) Interstitial defect (2) Frenkel defect
(3) Schottky defect (4) None of these
49. The second order Bragg diffraction of X-rays with λ =1.00 Å from a set of parallel planes in a metal occurs at an angle of 60°. The distance between the scattering planes in the crystal is
(1) 0.575 Å (2) 1.00 Å
(3) 2.00 Å (4) 1.15 Å
50. If we mix a pentavalent impurity in a crystal lattice of germanium, what type of semiconductor formation will occur?
(1) p-Type (2) n-Type
(3) Both (1) and (2) (4) None of the two