Chapter 9

The number of closest neighbours of a carbon atom in graphite is (a) 2 (b) 3 (c) 4 (d) 8

The low density of alkali metals is due to (a) their \(\mathrm{BCC}\) structure in which about \(32 \%\) of the available space is unfilled. (b) their HCP structure in which about \(74 \%\) of the available space is unfilled. (c) their cubic close packed (CCP) structure in which about \(74 \%\) of the available space is unfilled. (d) their \(\mathrm{BCC}\) structure in which about \(47 \%\) of the available space is unfilled.

The coordination number of a metal crystallizing in a HCP structure is (a) 12 (b) 4 (c) 8 (d) 6

Which of the following have the least void space fraction in their structure? (a) \(\mathrm{BCC}\) (b) \(\mathrm{BCC}\) and \(\mathrm{HCP}\) (c) \(\mathrm{HCP}\) (d) \(\mathrm{FCC}\) and \(\mathrm{HCP}\)

Which void is smallest in close packing? (a) tetrahedral (b) octahedral (c) cubic (d) square

Which of the following interstitial site is formed when the three closed packed spheres of one layer is put over three closed packed spheres of the second layer, their positions being inverted with respect to each other? (a) tetrahedral (b) octahedral (c) rhombohedral (d) tetragonal

In an FCC arrangement of metallic atoms, what is the relative ratio of the sizes of tetrahedral and octahedral voids? (a) \(0.543\) (b) \(0.732\) (c) \(0.414\) (d) \(0.637\)

Atoms of the element 'A' form HCP and atoms of element ' \(\mathrm{C}\) ' occupy only two-third of octahedral voids in it, then the general formula of the compound is (a) \(\mathrm{CA}\) (b) \(\mathrm{CA}_{2}\) (c) \(\mathrm{C}_{2} \mathrm{~A}_{3}\) (d) \(\mathrm{C}_{3} \mathrm{~A}_{2}\)

A solid has three types of atoms X, Y and Z. 'X' forms a FCC lattice with 'Y' atoms occupying all the tetrahedral voids and "Z' atoms occupying half the octahedral voids. The simplest formula of solid is (a) \(\mathrm{X}_{2} \mathrm{Y}_{4} \mathrm{Z}\) (b) \(\mathrm{XY}_{2} \mathrm{Z}_{4}\) (c) \(\mathrm{X}_{4} \mathrm{Y}_{2} \mathrm{Z}\) (d) \(\mathrm{X}_{4} \mathrm{YZ}_{2}\)

The ionic radii of \(\mathrm{Rb}^{+}\) and \(\mathrm{I}^{-}\) are \(1.46\) and \(2.16 \dot{\mathrm{A}}\), respectively. The most probable type of structure exhibited by it is (a) CsCl type (b) \(\mathrm{NaCl}\) type (c) \(\mathrm{ZnS}\) type (d) \(\mathrm{CaF}_{2}\) type

In the zinc blende structure \((\mathrm{ZnS}), \mathrm{S}^{2-}\) adopt CCP arrangement and \(\mathrm{Zn}^{2+}\) occupy (a) all octahedral voids (b) only \(50 \%\) of octahedral voids (c) only \(50 \%\) of tetrahedral voids (d) all tetrahedral voids

The number of nest nearest neighbours of \(\mathrm{Cs}^{+}\) ion in \(\mathrm{CsCl}\) crystal is (a) 12 (b) 8 (c) 6 (d) 4

In calcium fluoride structure, the coordination numbers of calcium and fluoride ions are, respectively, (a) 8 and \(\overline{4}\) (b) 6 and 8 (c) 4 and \(\overline{4}\) (d) 4 and 8

A binary solid \(\left(\mathrm{A}^{+} \mathrm{B}^{-}\right)\) has a rock salt structure. If the edge length is \(400 \mathrm{pm}\) and radius of cation is \(75 \mathrm{pm}\), the radius of anion is (a) \(100 \mathrm{pm}\) (b) \(125 \mathrm{pm}\) (c) \(250 \mathrm{pm}\) (d) \(325 \mathrm{pm}\)

Sodium oxide has anti-fluorite structure. The percentage of the tetrahedral voids occupied by the sodium ions is (a) \(12 \%\) (b) \(25 \%\) (c) \(50 \%\) (d) \(100 \%\)

CsBr has been structure with edge length 4.3. The shortest inter ionic distance in between \(\mathrm{Cs}^{+}\) and \(\mathrm{Br}^{-}\) is (a) \(3.72\) (b) \(1.86\) (c) \(7.44\) (d) \(4.3\)

\(\mathrm{NaCl}\) crystal is (a) FCC (b) \(\mathrm{BCC}\) (c) HCP (d) simple Cubic

A solid contains \(\mathrm{A}^{\mathrm{n}}\) and \(\mathrm{B}^{\mathrm{m}-}\) ions. The structure of solid is \(\mathrm{FCC}\) for \(\mathrm{B}^{\mathrm{m}-}\) ions and \(\mathrm{A}^{\mathrm{n}+}\) ions are present in one-fourth of tetrahedral voids as well as in one fourth of octahedral voids. What is the simplest formula of solid? (a) \(\mathrm{A}_{3} \mathrm{~B}_{4}\) (b) \(\mathrm{A}_{4} \mathrm{~B}_{3}\) (c) \(\mathrm{AB}_{2}\) (d) \(\mathrm{A}_{2} \mathrm{~B}\)

In a compound, oxide ions are arranged in CCP arrangement. Cations A occupy onesixth of the tetrahedral voids and cations B occupy one-third of the octahedral voids. The formula of the compound is (a) \(\mathrm{AB}_{2} \mathrm{O}_{4}\) (b) \(\mathrm{ABO}_{3}\) (c) \(\mathrm{ABO}_{2}\) (d) \(\mathrm{ABO}_{4}\)

Sapphire is aluminium oxide. Aluminium oxide crystallizes with aluminium ions in two-third of the octahedral voids in the closest packed array of oxide ions. What is the formula of aluminium oxide? (a) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{AlO}_{2}\) (c) \(\mathrm{Al}_{3} \mathrm{O}_{4}\) (d) \(\mathrm{Al}_{3} \mathrm{O}_{2}\)

What is the formula of the magnetic oxide of cobalt, used in recording tapes, that crystallizes with cobalt atoms occupying one-eighth of the tetrahedral holes and one half of the octahedral holes in a closest packed array of oxide ions? (a) \(\mathrm{Co}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{Co}_{5} \mathrm{O}_{s}\) (c) \(\mathrm{CoO}\) (d) \(\mathrm{Co}_{3} \mathrm{O}_{4}\)

Frenkel defect is noticed in (a) \(\mathrm{AgBr}\) (b) Zns (c) AgI (d) All

Schottky defect appears in (a) \(\mathrm{NaCl}\) (b) \(\mathrm{CsCl}\) (c) \(\mathrm{AgBr}\) (d) All

The yellow colour of \(\mathrm{ZnO}\) and conducting nature produced in heating is due to (a) Metal excess of defects due to interstitial cation (b) Extra positive ions present in an interstitial site (c) Trapped electrons (d) All

The intrinsic or thermodynamic defect is (a) Schottky defect (b) Metal excess defect due to excess cation (c) Metal excess defect due to anion vacancy (d) Metal-deficient defect

The only incorrect effect on density by the given defect in solids is (a) Density must decrease by vacancy defect. (b) Density must increase by interstitial defect. (c) Density must increase by impurity defect. (d) Density does not change by dislocation defect.

Which of the following is a ferromagnetic substance? (a) \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{Cr}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{Fe}_{3} \mathrm{O}_{4}\) (d) \(\mathrm{CrO}_{2}\)

Which of the following acts as a superconductor at \(4 \mathrm{~K}\) ? (a) \(\mathrm{He}\) (b) \(\mathrm{Cu}\) (c) \(\mathrm{K}\) (d) \(\mathrm{Mg}\)

Superconductors are substances which (a) conduct electricity at low temperatures. (b) conduct electricity at high temperature. (c) offer very high resistance to the flow of current. (d) offer no resistance to the flow of current.

Addition of arsenic in small amount to pure germanium will result in the formation of (a) \(\mathrm{n}\) -type semiconductor (b) germanium arsenide (c) p-type semiconductor (d) a superconducting alloy