Chapter 9

For a certain crystal, the unit cell axial lengths are found to be \(a=5.62 \AA, b=7.41\) \(\AA\) and \(c=10.13 \AA\). The three coordinate axes are mutually perpendicular. The crystal system to which the crystal belongs is (a) tetragonal (b) orthorhombic (c) monoclinic (d) cubic

Most crystals that show good cleavage because their atoms, ions or molecules are (a) weakly bonded together (b) strongly bonded together (c) spherically symmetrical (d) arranged in planes

Which of the following is the only incorrect statement regarding amorphous solids? (a) On heating, they may become crystalline at some temperature. (b) They may become crystalline on keeping for long time. (c) Amorphous solids can be moulded by heating. (d) They are anisotropic in nature.

A solid is soft, good conductor of electricity and has very high melting point. Its one of the allotropic forms is the hardest known substance. Hence, the solid is an example of (a) Ionic solid (b) Covalent solid (c) Molecular solid (d) Metallic solid

Silver (atomic mass \(=108\) ) has an atomic radius of \(144 \mathrm{pm}\) and density \(10.6 \mathrm{~g} / \mathrm{cm}^{3}\). To which type of cubic crystal silver belongs? (a) simple (b) \(\mathrm{BCC}\) (c) \(\mathrm{FCC}\) (d) end-centred

Constituent particles in quartz are bonded by (a) Electrovalent bonds (b) Covalent bonds (c) Van der Waal's forces (d) Metallic bonds

Gold crystallizes with FCC lattice for which the side length of the unit cell is \(5.0 \AA\). If the density of gold is \(10.5 \mathrm{~g} / \mathrm{cm}^{3}\) the value of Avogadro number is \((\mathrm{Au}=198)\) (a) \(6.022 \times 10^{23}\) (b) \(6.034 \times 10^{23}\) (c) \(5.966 \times 10^{23}\) (d) \(6.022 \times 10^{22}\)

What is the void space per unit cell for metallic silver crystallizing in the FCC system, the edge length of the unit cell being \(4 \AA\) ? (a) \(47.36 \AA^{3}\) (b) \(30.72 \AA^{3}\) (c) \(20.48 \AA^{3}\) (d) \(16.64 \AA^{3}\)

Which of the following is an example of metallic crystal solid? (a) \(\mathrm{C}\) (b) \(\mathrm{Si}\) (c) W (d) \(\mathrm{AgCl}\)

A metal exists as FCC crystal. If the atomic radius is \(100 \sqrt{2} \mathrm{pm}\) and the density of metal is \(12,500 \mathrm{~kg} / \mathrm{m}^{3}\), the metal is (Atomic masses: \(\mathrm{Ca}=40, \mathrm{Co}=58.9\), \(\left.\mathrm{Sn}=119.8, \mathrm{~Pb}=207.9 ; N_{\mathrm{A}}=6 \times 10^{23}\right)\) (a) Ca (b) \(\mathrm{Co}\) (c) Sn (d) \(\mathrm{Pb}\)

A solid element (monoatomic) exists in cubic crystal. If its atomic radius is \(1.0 \AA\) and the ratio of packing fraction and density is \(0.1 \mathrm{~cm}^{3} / \mathrm{g}\), then the atomic mass of the element is \(\left(N_{\mathrm{A}}=6 \times 10^{23}\right)\) (a) \(8 \pi\) (b) \(16 \pi\) (c) \(80 \pi\) (d) \(4 \pi\)

Iodine molecules are held in the crystal lattice by (a) London forces (b) Dipole-dipole interactions (c) Covalent bonds (d) Ionic bonds

The unit cell of highest symmetry is (a) cubic (b) triclinic (c) hexagonal (d) monoclinic

The unit cell of lowest symmetry is (a) cubic (b) triclinic (c) hexagonal (d) monoclinic

The densities of ice and water at \(0^{\circ} \mathrm{C}\) and 1 bar are \(0.96\) and \(0.99 \mathrm{~g} / \mathrm{cm}^{3}\), respectively. If the percentage of occupied space in ice is \(x\), then the percentage of empty space in water is (a) \(\frac{32}{33} x\) (b) \(\frac{33}{32} x\) (c) \(100-\frac{33}{32} x\) (d) \(100-\frac{32}{33} x\)

A match box exhibits \(\quad\) geometry. (a) cubic (b) orthorhombic (c) triclinic (d) monoclinic

The number of octahedral voids per unit \(\mathrm{BCC}\) cell is (a) \(1.0\) (b) \(2.0\) (c) \(1.5\) (d) 0

In a crystal, the atoms are located at the position of (a) zero potential energy (b) infinite potential energy (c) minimum potential energy (d) maximum potential energy

A metal having atomic mass \(60.22\) \(\mathrm{g} /\) mole crystallizes in \(\mathrm{ABCABC} \ldots\) type packing. The density of each metal atom if the edge length of unit cell is \(10 \AA\), is \(\left(N_{\mathrm{A}}=6.022 \times 10^{23}\right)\) (a) \(0.4 \mathrm{~g} / \mathrm{cm}^{3}\) (b) \(40 \mathrm{~g} / \mathrm{cm}^{3}\) (c) \(0.54 \mathrm{~g} / \mathrm{cm}^{3}\) (d) \(54 \mathrm{~g} / \mathrm{cm}^{3}\)

Packing fraction in \(2 \mathrm{D}-\) hexagonal arrangement of identical spheres is (a) \(\frac{\pi}{3 \sqrt{2}}\) (b) \(\frac{\pi}{3 \sqrt{3}}\) (c) \(\frac{\pi}{2 \sqrt{3}}\) (d) \(\frac{\pi}{6}\)

A close packing consists of a base of spheres, followed by a second layer where each sphere rests in the hollow at the junction of four spheres below it and the third layer then rests on these in an arrangement which corresponds exactly to that in the first layer. This packing is known as (a) \(\mathrm{HCP}\) (b) \(\mathrm{CCP}\) (c) square close packing (d) \(\mathrm{BCC}\) packing

If the height of \(\mathrm{HCP}\) unit cell of identical particles is \(h\), then the height of octahedral voids from the base is (a) \(\frac{h}{2}\) (b) \(\frac{h}{3}, \frac{2 h}{3}\) (c) \(\frac{h}{4}, \frac{3 h}{4}\) (d) \(\frac{h}{8}, \frac{7 h}{8}\)

Which of the following crystalline arrangement will have at least one of the angles equals to \(90^{\circ}\) and at least two axial lengths equal? (a) Orthorhombic (b) Rhombohedral (c) Monoclinic (d) Tetragonal

An element occurring in the body-centred cubic \((\mathrm{BCC})\) structure has \(1.208 \times 10^{23}\) unit cells. The total number of atoms of the element in these cells will be (a) \(2.416 \times 10^{23}\) (b) \(3.618 \times 10^{23}\) (c) \(6.04 \times 10^{22}\) (d) \(1.208 \times 10^{2.3}\)

An alloy of copper, silver and gold is found to have copper constituting the face-centred cubic (FCC) lattice. If silver atoms occupy the edge centres and gold is present at body centre, the alloy has a formula (a) \(\mathrm{Cu}_{4} \mathrm{Ag}_{2} \mathrm{Au}\) (b) \(\mathrm{Cu}_{4} \mathrm{Ag}_{4} \mathrm{Au}\) (c) \(\mathrm{Cu}_{4} \mathrm{Ag}_{3} \mathrm{Au}\) (d) \(\mathrm{CuAgAu}\)

A mineral having the formula \(\mathrm{AB}_{2}\) crystallizes in the CCP lattice, with the \(\mathrm{A}\) atoms occupying the lattice points. What is the coordination number of the B atoms? (a) 4 (b) 6 (c) 8 (d) 12

A solid PQ has rock salt type structure in which \(Q\) atoms are the corners of the unit cell. If the body-centred atoms in all the unit cells are missing, the resulting stoichiometry will be (a) \(\mathrm{PQ}\) (b) \(\mathrm{PQ}_{2}\) (c) \(\mathrm{P}_{3} \mathrm{Q}_{4}\) (d) \(\mathrm{P}_{4} \mathrm{Q}_{2}\)

There are three cubic unit cells \(\mathrm{A}, \mathrm{B}\) and C. A is FCC and all of its tetrahedral voids are also occupied. \(\mathrm{B}\) is also \(\mathrm{FCC}\) and all of its octahedral voids are also occupied. \(\mathrm{C}\) is simple cubic and all of its cubic voids are also occupied. If voids in all unit cells are occupied by the spheres exactly at their limiting radius, then the order of packing efficiency would be (a) \(\mathrm{A}<\mathrm{B}<\mathrm{C}\) (b) \(C

In a solid AB, having the \(\mathrm{NaCl}\) structure, A atoms occupy the corners of the cubic unit cell. If all the face-centred atoms along one of the axes are removed, then resulting stoichiometry of the solid is (a) \(\mathrm{AB}_{2}\) (b) \(\mathrm{A}_{2} \mathrm{~B}\) (c) \(\mathrm{A}_{4} \mathrm{~B}_{3}\) (d) \(\mathrm{A}_{3} \mathrm{~B}_{4}\)

Xenon crystallizes in FCC lattice and the edge of the unit cell is \(620 \mathrm{pm}\), then the radius of xenon atom is (a) \(219.20 \mathrm{pm}\) (b) \(438.5 \mathrm{pm}\) (c) \(265.5 \mathrm{pm}\) (d) \(536.94 \mathrm{pm}\)

Metallic gold crystallizes in FCC lattice with edge-length \(4.07\) ?. The closest distance between gold atoms is (a) \(3.525 \dot{\mathrm{A}}\) (b) \(5.714 \AA\) (c) \(2.857 \mathrm{~A}\) (d) \(1.428 \AA\)

Solid \(\mathrm{AB}\) has a rock salt type structure. If the radius of the cation is \(200 \mathrm{pm}\), what is the maximum possible radius of the anion? (a) \(483.1 \mathrm{pm}\) (b) \(273.6 \mathrm{pm}\) (c) \(200 \mathrm{pm}\) (d) \(400 \mathrm{pm}\)

The distance between two nearest neighbours in BCC lattice of axial length, \(l\), is (a) \(l\) (b) \(\frac{\sqrt{3}}{2} l\) (c) \(\frac{\sqrt{2}}{2} l\) (d) \(\frac{1}{2} l\)

The simplest formula of a solid having CCP arrangement for 'A' atoms in which alternate face-centres are occupied by 'B' atoms and alternate edge centres are occupied by 'C' atoms, is (a) \(\mathrm{ABC}\) (b) \(\mathrm{A}_{4} \mathrm{BC}\) (c) \(\mathrm{A}_{2} \mathrm{BC}\) (d) \(\mathrm{A}_{4} \mathrm{~B}_{2} \mathrm{C}\)

Sodium metal crystallizes in BCC lattice with the cell edge, \(a=4.29 \dot{\mathrm{A}}\). What is the radius of the sodium atom? (a) \(1.86 \dot{\mathrm{A}}\) (b) \(2.15 \dot{\mathrm{A}}\) (c) \(4.29 \mathrm{~A}\) (d) \(2.94 \dot{\mathrm{A}}\)

Spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged in CCP pattern. The normal spinel has one-eighth of the tetrahedral holes occupied by one type of metal ion and one-half of the octahedral hole occupied by another type of metal ion. Such a spinel is formed by \(\mathrm{Zn}^{2+}, \mathrm{Al}^{3+}\) and \(\mathrm{O}^{2-}\). The simplest formula of such spinel is (a) \(\mathrm{ZnAl}_{2} \mathrm{O}_{4}\) (b) \(\mathrm{Zn}_{2} \mathrm{AlO}_{4}\) (c) \(\mathrm{Zn}_{2} \mathrm{Al}_{3} \mathrm{O}_{4}\) (d) \(\mathrm{ZnAlO}_{2}\)

An ionic crystalline solid, \(\mathrm{MX}_{3}\), has a cubic unit cell. Which of the following arrangement of the ions is consistent with the stoichiometry of the compound? (a) \(\mathrm{M}^{3+}\) ions at the corners and \(\mathrm{X}^{-}\) ions at the face centres (b) \(\mathrm{M}^{3+}\) ions at the corners and \(\mathrm{X}^{-}\) ions at the body centres. (c) \(\mathrm{X}^{-}\) ions at the corners and \(\mathrm{M}^{3+}\) ions at the face centres. (d) \(\mathrm{X}^{-}\) ions at the corners and \(\mathrm{M}^{3+}\) ions at the body centres.

An element (atomic mass = 100 ) having BCC structure has unit cell edge length \(400 \mathrm{pm}\). The density of this element will be \(\left(N_{\Lambda}=6 \times 10^{23}\right)\) (a) \(5.2 \mathrm{~g} / \mathrm{m}\) (b) \(10.4 \mathrm{~g} / \mathrm{ml}\) (c) \(0.42 \mathrm{~g} / \mathrm{ml}\) (d) \(2.6 \mathrm{~g} / \mathrm{ml}\)

Potassium has BCC structure with nearest neighbour distance \((2.5 \times \sqrt{3}) \dot{A}\). Its density will be \(\left(\mathrm{K}=39, N_{\mathrm{A}}=6 \times 10^{23}\right)\) (a) \(1.040 \mathrm{~kg} / \mathrm{m}^{3}\) (b) \(104 \mathrm{~kg} / \mathrm{m}^{3}\) (c) \(520 \mathrm{~kg} / \mathrm{m}^{3}\) (d) \(1040 \mathrm{~kg} / \mathrm{m}^{3}\)

FeO crystallizes in the cubic system, in which there is four formula units in each unit cell. The density of the crystal is \(4.0 \mathrm{~g} / \mathrm{cm}^{3} .\) The side length of each unit cell is \(\left(\mathrm{Fe}=56, N_{\mathrm{A}}=6 \times 10^{23}\right)\) (a) \(4.227 \AA\) (b) \(2.424 \AA\) (c) \(4.932 \AA\) (d) \(2.974 \AA\)

In an ionic solid \(\mathrm{AB}_{2} \mathrm{O}_{4}\), the oxide ions form CCP. 'A' and 'B' are metal ions in which one is bivalent and another is trivalent (not necessarily in given order). If all the bivalent ions occupy octahedral holes and the trivalent ions occupy tetrahedral and octahedral voids in equal numbers, then the fraction of octahedral voids unoccupied is (a) \(\frac{1}{2}\) (b) \(\frac{3}{4}\) (c) \(\frac{1}{4}\) (d) \(\frac{7}{8}\)

\(\alpha\) -form of iron exists in BCC form and \(\gamma\) -form of iron exists in FCC structure. Assuming that the distance between the nearest neighbours is the same in the two forms, the ratio of the density of \(\gamma\) form to that of \(\alpha\) -form is (a) \(4 \sqrt{2}: 3 \sqrt{3}\) (b) \(4 \sqrt{3}: 3 \sqrt{2}\) (c) \(\sqrt{3}: \sqrt{2}\) (d) \(2: 1\)

Packing fraction in simple cubic lattice is (a) \(\frac{1}{6} \pi\) (b) \(\frac{\sqrt{2}}{6} \pi\) (c) \(\frac{\sqrt{3}}{8} \pi\) (d) \(\frac{1}{2} \pi\)

Which of the following oxide shows electrical properties like metals? (a) \(\mathrm{SiO}_{2}\) (b) \(\mathrm{MgO}\) (c) \(\mathrm{SO}_{2}(\mathrm{~s})\) (d) \(\mathrm{CrO}_{2}\)

Packing fraction in \(\mathrm{BCC}\) lattice is (a) \(\frac{1}{6} \pi\) (b) \(\frac{\sqrt{2}}{6} \pi\) (c) \(\frac{\sqrt{3}}{8} \pi\) (d) \(\frac{\sqrt{3}}{2} \pi\)

Which kind of defects is introduced by doping in silicon crystal? (a) Dislocation defect (b) Schottky defect (c) Frenkel defect (d) Electronic defect

Packing fraction in FCC lattice is (a) \(\frac{1}{6} \pi\) (b) \(\frac{\sqrt{2}}{6} \pi\) (c) \(\frac{\sqrt{3}}{8} \pi\) (d) \(\frac{\sqrt{2}}{3} \pi\)

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because (a) all the domains get oriented in the direction of magnetic field. (b) all the domains get oriented in the direction opposite to the direction of magnetic field. (c) domains get oriented randomly. (d) domains are not affected by magnetic field.

Number of carbon atoms per unit cell of diamond is (a) 4 (b) 6 (c) 8 (d) 12

The number of closest neighbours of a carbon atom in diamond is (a) 2 (b) 4 (c) 6 (d) \(\underline{8}\)