12th Class Chemistry The Solid State / ठोस प्रावस्था Question Bank

done Case Based (MCQs) - The Solid State Total Questions - 25

• question_answer1)

  Directions: (Q. 1 to 5)

  Case I: Read the passage given below and answer the following questions from 1 to 5.

  In hexagonal system of crystals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are regular hexagons and three atoms are sandwiched in between them. A space-filling model of this structure, called hexagonal close packed (hcp), is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spheres are then placed over the first layer so that they touch each other and represent the second layer. Each one of these three spheres touches three spheres of the bottom layer.

  Finally, the second layer is covered with a third layer that is identical to the bottom layer in relative position.

  The number of atoms in this hcp unit cell is
  A)
  4 done clear
  B)
  6 done clear
  C)
  12 done clear
  D)
  17 done clear
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• question_answer2)
  The volume of this hcp unit cell is
  A)
  \[24\sqrt{2}{{r}^{3}}\] done clear
  B)
  \[16\sqrt{2}{{r}^{3}}\] done clear
  C)
  \[12\sqrt{2}{{r}^{3}}\] done clear
  D)
  \[\frac{64}{3\sqrt{3}}{{r}^{3}}\] done clear
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• question_answer3)
  The empty space in this hcp unit cell is
  A)
  74% done clear
  B)
  47.6% done clear
  C)
  32% done clear
  D)
  26% done clear
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• question_answer4)
  Which of the following statements is correct about hexagonal close packing?
  A)
  In this arrangement, third layer is identical to the first layer. done clear
  B)
  The coordination number in this arrangement is 6. done clear
  C)
  It is as closely packed as body centered cubic packing. done clear
  D)
  It has 32% empty space. done clear
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• question_answer5)
  In hexagonal close packing of spheres in three-dimensions
  A)
  in one unit cell there are 12 octahedral voids and all are completely inside the unit cell done clear
  B)
  in one unit cell there are six octahedral voids and all are completely inside the unit cell done clear
  C)
  in one unit cell there are six octahedral voids out of which three are completely inside the unit cell and other three are from contributions of octahedral voids which are partially inside the unit cell done clear
  D)
  in one unit cell there are 12 tetrahedral voids, all are completely inside the unit cell. done clear
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• question_answer6)

  Directions: (Q. 6 to 10)

  Case II: Read the passage given below and answer the following questions.

  In an assembly of atoms or molecules, a solid phase is formed whenever the interatomic attractive forces significantly exceed the disruptive thermal forces and thus restrict the mobility of atoms, forcing them into more or less fixed positions. From energy considerations, it is evident that in such solids the atoms or molecules will always attempt to assume highly ordered structures which are characterised by symmetry. Depending on the nature of the active interatomic forces, all solids may be subdivided into the following categories:

  Ionic solids: These solids consist of positively and negatively charged ions arranged in a regular fashion throughout the solid. These solids are very hard and brittle, have very high melting points and have high enthalpies of vaporisation, e.g., NaCl, MgO, KCl, LiCl, etc.

  Covalent solids: In these solids, the constituent particles are atoms which are linked together by a continuous system of covalent bonds. These bonds are strong and directional in nature. The covalent crystals are hard, have high melting points, are poor conductors of electricity. Diamond is a typical example of covalent solids.

  Metallic solids: In these solids, the constituent particles are positive ions immersed in a sea of mobile electrons. Metallic solids may be hard as well as soft. They are good conductors of heat and electricity e.g., common metals such as nickel, copper and alloys.

  Molecular solids: In these the constituent particles are molecules. The molecules are held together by dispersion forces or London forces, dipole-dipole forces or hydrogen bonds.

  In the following questions (Q. No. 6-10), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage

  Assertion: Molecular solids are characterized by low melting point.

  Reason: Molecular solids are made up of covalent molecules.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer7)

  Assertion: Ionic solids are characterized by high melting and boiling point.

  Reason: Ionic solids have coulombic forces of attraction between their ions.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer8)

  Assertion: Covalent solids are insulators of electricity.

  Reason: Covalent solids are constituted by ions.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer9)

  Assertion: Diamond and graphite do not have the same covalent structure.

  Reason: Silicon carbide is typical example of network solid.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer10)

  Assertion: Covalent solids have high melting points.

  Reason: Covalent solids have strong electrostatic forces of attraction.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer11)

  Directions: (Q. 11 to 15)

  Case III: Read the passage given below and answer the following questions from 11 to 15. The adjective, 'crystalline' when applied to solids, implies an ideal crystal in which the structural units, termed as unit cells, are repeated regularly and indefinitely in three dimensions in space. The unit cell, containing at least one molecule, has a definite orientation and shape defined by the translational vectors, a, b and c.

  The unit cell therefore has a definite volume, V that contains the atoms and molecules necessary for generating the crystal. Every crystal can be classified as a member of one of the seven possible crystal systems or crystal classes that are defined by the relationships between the individual dimensions, a, b and c of the unit cell and between the individual angles, \[\alpha \], \[\beta \] and \[\gamma \] of the unit cell. The structure of the given crystal may be assigned to one of the 7 crystal systems, to one of the 14 Bravais lattices, and to one of the 230 space groups. These uniquely define the possible ways of arranging atoms in a three-dimensional solid. Based on these observations, seven crystal systems were identified: triclinic, monoclinic, trigonal or rhombohedral, tetragonal, hexagonal, rhombic or orthorhombic and cubic.

  The crystal system of a compound with unit cell dimensions, a = 0.387 nm, b = 0.387 nm and c = 0.504 nm and \[\alpha =\beta =90{}^\circ \]and \[\gamma =120{}^\circ \]is
  A)
  cubic done clear
  B)
  hexagonal done clear
  C)
  orthorhombic done clear
  D)
  rhombohedral. done clear
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• question_answer12)

  The unit cell with the structure given below represents ____ crystal system.

  A)
  cubic done clear
  B)
  orthorhombic done clear
  C)
  tetragonal done clear
  D)
  trigonal done clear
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• question_answer13)
  In a triclinic crystal
  A)
  \[a=b=c,\,\alpha =\beta =\gamma \ne 90{}^\circ \] done clear
  B)
  \[a\ne b=c,\,\alpha =\beta =\gamma =90{}^\circ \] done clear
  C)
  \[a\ne b\ne c,\,\,\alpha \ne \beta \ne \gamma \ne 90{}^\circ \] done clear
  D)
  \[a\ne b\ne c,\,\,\alpha =\gamma =90{}^\circ ,\,\beta \ne 90{}^\circ \] done clear
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• question_answer14)
  The unit cell with dimensions \[\alpha =\beta =\gamma =90{}^\circ \,\,\,a=b\ne c\] is
  A)
  cubic done clear
  B)
  triclinic done clear
  C)
  hexagonal done clear
  D)
  tetragonal. done clear
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• question_answer15)
  An example of orthorhombic crystal system is
  A)
  \[Sn{{O}_{2}}\] done clear
  B)
  \[KN{{O}_{3}}\] done clear
  C)
  \[ZnO\] done clear
  D)
  \[{{K}_{2}}C{{r}_{2}}{{O}_{7}}\] done clear
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• question_answer16)

  Directions: (Q. 16 to 20)

  Case IV: Read the passage given below and answer the following questions.

  Most important crystal lattices are the simple cubic, body centred cubic and face centred cubic.

  In simple cubic lattice, all the atoms are present at all the corners of the cube. In body-centred cubic lattice, atoms are present at all the corners and at the body-centre. In face-centred cubic lattice, atoms are present at the corners and at the centers of all six faces.

  In the formation of crystals, the constituent particles get closely packed together. The closely packed arrangement is that in which maximum available space is occupied leaving minimum vacant space. The most efficient close packing, can be achieved in two ways, one which is called hexagonal close packing (hcp) and the other, cubic close packing (ccp or fcc).

  In the following questions (Q. No. 16-20), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.

  Assertion: Face centred cubic cell has atoms per unit cell.

  Reason: In fcc unit cell, there are 8 atoms at the corners and 6 atoms at face centres.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer17)

  Assertion: CsCl has body-centred cubic arrangement.

  Reason: CsCl has one \[C{{s}^{+}}\] ion and 8 \[C{{l}^{-}}\] ions in its unit cell.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer18)
   

  Assertion: fcc and hcp have same packing efficiency.

  Reason: bcc and fcc both have same number of atoms per unit cell and same arrangement.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer19)

  Assertion: The total number of atoms present in a simple cubic unit cell is one.

  Reason: Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer20)

  Assertion: The packing efficiency is maximum for the fcc structure.

  Reason: The coordination number is 12 in fcc structures.

  A)
  Assertion and reason both are correct statements and reason is correct explanation for assertion. done clear
  B)
  Assertion and reason both are correct statements but reason is not correct explanation for assertion. done clear
  C)
  Assertion is correct statement but reason is wrong statement. done clear
  D)
  Assertion is wrong statement but reason is correct statement. done clear
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• question_answer21)

  Directions: (Q. 21 to 25)

  Case V: Read the passage given below and answer the following questions from 21 to 25.

  In an ideal crystal, there must be regular repeating arrangement of the constituting particles and its entropy must be zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal, these defects arises either due to disorder or dislocation of the constituting particles from their normal positions or due to the movement of the particles even at absolute zero temperature.

  Such defects increase with rise in temperature. In addition to this, certain defects arise due to the presence of some impurities. Such defects not only modify the existing properties of the crystalline solids but also impart certain new characteristics to them.

  AgCl is crystallised from molten AgCl containing a little\[CdC{{l}_{2}}\]. The solid obtained will have
  A)
  cationic vacancies equal to number of \[C{{d}^{2+}}\]ions incorporated done clear
  B)
  cationic vacancies equal to double the number of \[C{{d}^{2+}}\] ions done clear
  C)
  anionic vacancies done clear
  D)
  neither cationic nor anionic vacancies. done clear
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• question_answer22)
  Lattice defect per \[{{10}^{15}}\] NaCl is 1. What is the number of lattice defects in a mole of NaCl?
  A)
  \[6.02\times {{10}^{23}}\] done clear
  B)
  \[6.02\times {{10}^{8}}\] done clear
  C)
  \[{{10}^{14}}\] done clear
  D)
  None of these done clear
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• question_answer23)
  The ionic substances in which the cation and anion are of almost similar size shows
  A)
  non-stoichiometric defect done clear
  B)
  Schottky defect done clear
  C)
  Frenkel defect done clear
  D)
  all of these. done clear
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• question_answer24)
  If \[A{{l}^{3+}}\]ions replace \[N{{a}^{+}}\] ions at the edge centres of NaCl lattice, then the number of vacancies in 1 mole of NaCl will be
  A)
  \[3.01\times {{10}^{23}}\] done clear
  B)
  \[6.02\times {{10}^{23}}\] done clear
  C)
  \[9.03\times {{10}^{23}}\] done clear
  D)
  \[12.04\times {{10}^{23}}\] done clear
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• question_answer25)
  Which of the following gives both Frenkel and Schottky defect?
  A)
  AgCl done clear
  B)
  CsCl done clear
  C)
  KCl done clear
  D)
  AgBr done clear
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