Chp. Solid States Notes (Chemistry)

1. SOLID STATE
SYNOPSIS
Introduction
A solid is a form of matter which possesses a
definite shape and volume.
In case of solids, the inter particle forces are
strong. Hence, the constituent particles are
very closely packed.
The constituent particles possess fixed
positions within the solid and can only
oscillate about their mean positions.
Gharacteristic Properties of Sol ids
(i) Definite shape and volume.
(ii) High density.
(iii) Possess rigidity.
(iv) Are incompressible.
Types of Solids
1. Crystalline solids
2. Amorphous solids
Crystalline Solids
The various constituent p article s are
arranged in a definite geometric pattern in three
dimensional space. They possess long range and
short range order.
Amorphous Solids
The constituent particles are not arranged
in a regular manner. Hence there is only a short
range order.
Cr5rstalline Solid Amorphous Solid
1. Constituent particles are arranged in a regular
manner hence there is short range as well as
long range order.
2. Definite, sharp melting point (heat of fusion is
definite).
3. They are anisotropic.
4. They undergo a clean cleavage.
5. They are true solids.
6. Examples .' Ice, NaCl, Na, gold, copper, dia-
mond, graphite, ceramics.
1. Constituent particles are not arranged in any
regular fashion hence there is only short range
ord er.
2. They melt over a range of temperature (heat
of fusion is not definite).
3. They are isotropic.
4. They undergo an irregular cut.
5. They are pseudo solids or supercooled liquids.
6. Examples : Glass, plastic, rubber, tat, metallic
glass.
Anisotropy
The properties like refractive index, electrical
conductivity, density etc. have different values in
different directions.
lsotropy
The properties like density, refractive index,
electrical conductivity etc. are identical in all
directions fiust like gases or liquids).
Crystallites
Due to short range order possessed by
amorphous solids small regions within the
amorphous solids may be crystalline while the rest
may be non-crystalline.
These crystalline parts of the antorphous
solid are called crystallites.
t
+
+

2. MHT-CET + CHEMISTRY
lsomorphism
Two or more substances having the sarne
crystal structure are said to be isomorphous.
Isomorphous substances have the Eqme atomic
ratio.
Eryamples : NaF and MgO [atomic ratio 1 : 1],
NaNO3 and CaCO3 [atomic ratio 1 : 1 : 3] .
Polymorphism
A single substance that exists in two or more
forms or crystalline structures is said to be
polymorphous. Polymorphs of a substance are
formed under different conditions.
Polymorphs of an element are called
allotropes.
Examples ; Calcite and argonite are two
forms of calcium carbonate.
o-quartz, B-quartz andcristobalite are forms
of silica.
Diamond, graphite and fullerene are
allotropic forms of carbon.
Classification of Crystalline
Solids
(Based on the nature of constituent particles
and the forces present between them)
(l) lonic Solids
(NaCl, K2SO+, CaF2, KCI)
(i) Constituent particles are ions of opposite
charge.
(ii) Particles held together by electrostatic
(coulombic) force.
(iii) Non conductors of electricity in the solid
state. However they are good conductors
when melted or dissolved in water.
Solid State
(iv) Due to strong electrostatic forces ions are
closely packed and hence ionic solids are
hard.
(v) They are brittle as stability depends on
preservation of their geometric arrange-
ment.
(vi) High melting and boiling points.
(!l) Molecular Solids
(CIz , H2, CH+, COz, O2 on solidification and
crystalline organic compounds)
(i) Constituent particles are molecules or
unbonded single atoms of the same
substance. (in case of inert gases)
(ii) Soft solids with low melting points due
to weak intermolecular forces.
(iii) Poor electrical conductors and good
insulators.
(iv) Intramolecular forces (within the mol-
ecule) are covalent bonds.
(v)'Ji,::T,:l;;lT.rorces (between the
(a) Weak dipole - dipole interaction (in
case of polar molecules)
e.g., So1id HCl, HzO, SOz
(b) Very weak dispersion or London
forces (in case of non-polar molecules)
e.g., CH4,Hz, Ar, Ne.
(c) Intermolecular hydrogen bonds.
e.9., HzO (ice), NHg, HF.
(!ll) Metallic Solids
(Metals such as Na, K, Ca, Li, Fe, Au, Ag,
co)
Crystalline solids formed by atoms of the
same metallic element held together by
a metallic bond.
Malleable and ductile.
Good electrical and thermal (heat)
conductivity.
In case of solid metal, the valence electrons
are loosely held and are hence delocalised
over the entire crystal. Hence the crystal is
considered to be an array of positive ions in
a sea of mobile electrons. The attractive
interactions between the cations and the
(i)
(ii)
(iii)
Crystalline solid
Covalent
solids
(Network
solids)
Metallic
solids
Molecular
solids
Hydrogen
bonded
molecular
solids
Polar
molecular
solids
Non-polar
molecular
solids

3. MHT-CET
+ CHEMISTRY
mobile electrons constitute the metallic
bonds.
(lV) Govalent Network Grystals
(Diamond, quartz (SiO2), boron nitride,
carborandum)
(i) Constituent particles are atoms which
are linked by a continuous system of
covalent bonds.
Due to the continuous linking of atoms
there is a rigid three dimen,sional
structure which behaves at a single
giant molecule.
Hardest and most incompressible solids.
High melting and boiling points.
Electrons are localised and not mobile
hence they are poor conductions of heat
and electricity.
Crystal Structure
The orciered three dimensional arrangement
of particles in a crystal is described using two
terms : (i) lattice, (ii) basis.
Solid State
Unit Cell
The smallest repeating structural unit of a
crystalline solid is called unit cell.
When unit cells repeat in three dimensions
it generates the entire crystal. When unit cells are
stacked together to generate a crystal, each unit
ceII shares its faces, edges and corners with
neighbouring unit cells.
The geometric shape of the unit cell will be
the same as that of the macroscopic crystal.
The dimensions of the unit ceII along the
three axes are denoted as fl, b, and c. The angles
between these axes are represented by the symbols
u, B, and y.
Unit cell parameters
The angle between a and b is y.
The angle between b and c is ct.
The angle between a and c is $.
Types of Unit Cells
(i) Primitive or simple unit cell
The constituent particles are present only at
the corners of the unit cell.
(ii) Body-centred unit cell
The constituent particles are present at the
corners of the unit ceJI and one particles is
present at the centre of its body.
(iii) Face centred unit cell
The constituent particles are present at the
corners of the unit cell as well as the centres
of each of the faces.
(iv) Base-centred or end centred unit cell
The constituent particles are present at the
corners of the unit cell as well as at the centre
of any two of its opposite faces.
(ii)
(iii)
(iv)
(v)
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o
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a
Lattice
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Crysta ! structu re
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Crystal
Lattice
A lattice is a geometrical arrangement of
points in a three dimensional periodic array.
A crystal structure is obtained by attaching
a constituent particle to each of the lattice
points.
The constituent particles that are attached
to the lattice points form the basis of the
crystal lattice (space lattice).
Hence, the structure which results by
attaching abasis to each of the lattice points
is called a crystal.
+

4. MHT-CET + GHEMISTRY
CrystalSystems
+ There are only 14 different ways in which similar points can be arranged in
order. These 14 different arrangements which describe the crystal structure
Solid State
a three dimensional
are called Brauois
lattices (unit cells).
i The possible combination of values of a, b, c, and o, 0, y give rise to seven crystal systems which then
are further classified as primitive, body centred, face centred etc.
The seven crystal systems are : Cubic, Tetragonal, Orthorhombic, Rhombohedral, Monoclinic, Triclinic
and Hexagonal system.
Crystat sysfem
Bravais lattices
Name Unit cell structure
1. Cubic (i) Simple or primitive
(ii) Body centred
(iii) Face centred
(ii) (iii)
2. Orthorhombic (i) Simple or primitive
(ii) Body centred
(iii) Face centred
(iv) Base centred or
end centred
(ii) (iii) (iv)
3. Tetragonal (i) Simple or primitive
(ii) Body centred
(ii)
4. Monoclinic (i) Simple or primitive
(ii) Base centred or
end centred
(ii)
5. Rhombohedral (i) Simple or primitive
contd. on next page
-

5. ilHT-CET
+ CHEMISTRY
(i) Simple or primitive
e Triclinic
7. Hexagonal (i) Simple or primitive
Solid State
Cubic SYstem
The three types of unit cells in the cubic system are
-
(i) Primitive or simple cubic (SC)
(ii) Body centred cubic (BCC)
(iii) Face centred cubic (FCC).
Each corner particle ofa cube is shared by 8 cubes; hence it contributes 1/8th to a given unit ceII.
Each face centred atom is shared by two cubes and hence it contributes ll2 of itself to a given unit
ceII.
Each edge particle is shared by four unit cells hence it contributes 1/4th of itself to a given unit cell.
Packing of Particles in a Crystal Lattice
+ Constituent particles are considered as hard spheres. Since the constituent particles are closely
packed the interparticle attractions are maximum.
+ The numbers of neighbouring spheres which touch any given sphere is its coordination nurnber
(c/f).
<) The greater the coordination number the closer are the spheres and greater is the compactness of
packing.
+
+
Simp:Ie Cub,ib, C:eXI Bod'y Centred Cubic CelX Faee :,C$ntibd Cubid,... $retrtr:
1. Constituent particles at the
corners of the unit cell.
2. Number of atoms per unit cell
is 1.
3. Packing efficiency is 52 .36%.
4. Densit
M
v=;,l/o
1. Constituent particles at the
corners of the unit cell and
one at the body centre posi-
tion.
2. Number of atoms per unit cell
is 2.
3. Packing efficiency - 68Yo.
2M
4. Density =;*
Constituent particles at the
corners of the unit cell and
one each at the face centres.
2. Number of atoms per unit cell
is 4.
3. Packing efficiency LS 74oh.
4. Densit
4 M
v=;m
l

6. MHT.CET + GHEMISTRY
Close Packed Structures
(A) CIose Packing in One Dimension
There is only one way in which spheres can
be arranged it one dimensional structure. The
spheres should touch each other in a row. Since
each sphere touches two neighbouring spheres;
coordination number is 2.
Close packing in one dimension
(B) Close Packing in Two Dimensions
When the rows are stacked over each other a
two dimensional close packed structure (crystal
plane) is obtained. This arrangelnent is possible
in either of two ways.
Square Close Packing
(i) H orizontally and vertically aligned
(AAAA type) : The spheres in the second row are
placed so that they are touching the spheres of
the first row and are exactly above the spheres of
the first row. Coordination number is 4.
A layer
A layer
A layer
A layer
Square close packing
(ii) Hexagonal Close packing (ABAB
type) : The second row is arranged in a way that
its spheres fit in the depressions of the first row.
Coordination number is 6.
Since the free space (voids) in this arrange-
ment is lesser; it is more efficient packing. The
voids are triangular in shape and the apex of the
triangular voids in alternate rows points upwards
and downwards.
A layer
B layer
A layer
B layer
Hexagonal close packing in two dimension
(C) Close Packing in Three Dimension
+ Obtained by stacking of two dimensional
layers.
Solid State
+ Two dimensional square packed layers can
be stacked in only one way.
+ Two dimensional hexagonal close packed lay-
ers can be stacked in two ways as hexagonal
close packed (hcp) and cubic close packed
(ccp) structures.
(a) Stacking of square close packed layers
(AAAA type)
Square close packed layers are placed in
a way so that the spheres of the second
Iayer are placed exactly above the first
Iayer. Hence there is horizontal and
vertical alignment resulting in a simple
cubic structure
Its unit cell is the primitiue cubic urtit
cell.
Coordination number is 6.
Polonium is the only metal uthich
crystallises in simple cubic close packed
structure.
A layer
A layer
A layer
A la5,er:
Stacking of square closed packed layers
(b) Stacking of two hexagonal close packed
structures
the depressions of the first layer.
are not covered by the spheres of the
second layer.
the spheres of the second layer generate
tetrahedral uoids.
first layer have above them the triangtr'
Iar voids of the second layer.
Two layers of closed packed spheres

7. MHT-C
ET + CHEMISTRY
The ouerlapping triangular uoids from
the two layers together form an octahe-
dral uoid which ls surrounded by six
spheres.
Tetrahedral and Octahedral voids
A tetrahedral void is surrounded by four
spheres. (CN = 4)
On joining the centres of these four
spheres a tetrahedron if formed which
enclose a tetrahedral void.
An octahedral void is surrounded by six
spheres. (CN = 6)
On joining the centres of these six
spheres an octahedron is formed; which
encloses an octahedral void.
The depressions in which spheres of the
second layer rest are tetrahedral uoids
uthile the depression in which no spheres
rest are octahedral uoids.
Solid State
or the second layer. The spheres of the
fourth layer are aligned with the spheres
of the first layer resulting tn ABCABC
type of arrangement and gives a cubic
close packed (ccp) structure.Its unit cell
ts FCC type.
In both hcp and ccp/fcc structures; each
sphere ls surrounded by 12 neighbouring
spheres, 6 in its own layer; 3 aboue and 3
below. Hence coordination number is 12.
ep
ffi
ffie
qp
M
ffiffim
Expanded
view (a)
Expanded
view (b)
Formation of hexagonal closed packed structures
Number of voids per atom
+ Both octahedral and tetrahedral voids are
present in hcp and ccplfcc structures.
+ There are two tetrahedral and one octahedral
uoid per atom.
+ If x denotes the number of atoms in the
structure then the number of tetrahedral
voids ts 2x and the number of octahedral voids
is r.
Packing Efficiency and
Packing Fraction
+ Packing efficiency is the percentage of the
total space occupied by the spheres (par-
ticles).
+ Packing fraction is the fraction of the total
space occupied by the constituent particles.
Packing efficiency = Packing fraction X 100
Packing fraction
Volume occupied by the
particles in the unit cell
Total volume of unit cell
g*:*A
Tetrahedron
Tetrahedral void
Octrahedral N
hole
Octrahedron
Octahedralvoid
(c) Placing the third hexagonal close
packed layer
There are two ways of placing the third hex-
agonal close packed layer on the second.
(i)
*l':ruHffJJHn Tif ,#:l ';fi:
results in ABAB arrangement and gives
a hexagonal close packed (hcp) structu,re.
(ii) By covering the octahedral voids of the
second layer by the spheres of the third
Iayer.
In this case the spheres of the third layer
do not align with the spheres of the first
+
+

8. IVIHT.CET + CHEMISTRY
Crystal Defects or Imperfections
+ Irregularities or disorder during the stacking
of atoms gives rise to defects or imperfections
in the crystal lattice.
+ The faster the crystallisation of the solid the
greater are the defects created.
+ Ideal crystals with no defects are possible
only at the absolute zero temperature.
+ Defects may be intentionally created to
rnodify certain properties of the crystal.
+ Whatever the type of defect; electrical neu-
trality is always maintained.
+ The types of defects possible are point, line
and plane defects.
Point Defects
The defects produced due to an irregularity
produced because of arrangement of the basis at
lattice points.
The three main types of point defects are
(D Stoichiometric point defects.
(ID Impurity defects.
(IID Non stoichiometric point defects.
Stoichiometric Point Defects
AIso calIed intrinsic or thermodynamic
defects.
The defects in which the ratio between the
cations and anions remains the same as
represented by the molecular formula.
The stoichiometry of the compound is not
changed.
Four types of stoichiometric point defects
(a) Vacancy defect
lar site in a crystal lattice it creates a
vacant lattice site. This creates a vacancy
defect.
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Solid State
crystallisation or by heating a solid or by
absorption of heat from the surrounding.
volume remains the same. Hence, the
density of the solid decreases.
(b) Self Interstitial defect
a crystal are called interstitial spaces.
tial sites in a crystal structure it is called
interstitial defect.
(i) An extra particle occupies an empty
interstitial space in the crystal lattice.
This extra particle is the same as those
already present in the crystal lattice. In
this case the density increq,ses as there
is an increase in mass due to the extra
particles.
(r)
+
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ot-oooo
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Self interstitial effect
(ii) The secorud way in which the interstitial
defect occurs is when a particle gets
shifted from its original lattice point and
occupies an interstitial space in the
crystal.
In this case when the particle is displaced
to the interstitial site ? a vacancy is
created at the original site. Ilence this is
a combination of uacancy defect and self
interstitial defect.
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oo
Vacancy
Interstitial
atom
Vacancy defect
Vacancy
Vacancy defect and self interstitial defect

9. MHT-CET
+ CHEMISTRY
The density of the substance remains t
same.
(c) SchottkY defect
In an ionic solid equal number of cations
and anions are missing from their regular
positions in the crystal lattice creating
vacancies.
Since it is a paired cation-anion vacancy
defect it is also called a pair defect.
There exist two holes per ion pair lost.
This type of defect is shown by ionic
compounds which have;
High ionic character; high coordination
number of anion and small difference
between size of cation and anion.
Cation vacancy
Schottky defect
Consequences of Schottky Defect :
decreases with the volume remaining
same. Henc e, density decreases.
anions is missing; the electrical rueutrality
is preserved.
crystals s uch as lliaCl, AgBr and KCl.
(d) Frenkel defect
an ionic compound leaves its regular lat-
tice site and occupies interstitial position
between lattice points.
hence cations occupy interstitial sites.
Since the smaller cation is displaced from its
normal site there is a vacancy in the original
site. Henc e, Frenkel defect is a combination
of uacanq) defect and interstitial defect.
Solid State
This type of defect is shown by ionic
compounds which have : ions with low
coordination number and large difference
between size of cation and anion.
Vacancy of cation
Cation at
interstitial site
Vacancy
of cation
Frenkel defect
Consequences of Frenkel defect
lattice the density is unchanged.
because cations and anions are present
in equal number.
ZnS, AgCl, AgBr, AgI, Caf 2.
(ll) lmpurity Defect
+ This defect occurs when foreign atoms (atoms
different from host atoms) are present in the
crystal lattice.
Two kinds of impurity defects are substitu-
tional and interstitial impurity defects.
Substitutional Impurity Defect
In this case; the foreign atoms are found
at the lattice sites in place of host atoms.
Hence, regular atoms are displaced from
their lattice sites by impurity atoms.
This type of defect is possible when the
atoms of the host and impurity element
have almost same size.
For example, solid solutions (alloys).
Brass (alloy of Cu and Zn) has host atoms
of Cu and Znbehaves as foreign atoms.
Example ; Vacancy through aliovalent
impurity.
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+
(a)
OoO 7
O@
oOoJ)oO
O@Q-oOo
oO -OoO
O@Oe;Qo
oOoOrO
OoO./Oo
oO@ Y oO
O .OoOo
oOrO@O
Anion vacancy
I

10. MHT-CET + CHEMISTRY
Vacancy of Nae ion
Vacancy through aliovalent ion
An aliovalent ion has an oxidation state
different from that of the host ion.
A vacancy can be created by addition of
impurities of aliovalent ions.
If SrCl2 is added to NaCI during its
crystallization; the Sr2
*
ions replace Na*
ions. However to maintain electrical
neutrality; one Sr2
*
ion replaces two Na*
ions and thus creates one vacant site.
(b) lnterstitial impurity defect
interstitial spaces in the lattice structure.
the lattice sites and carbon atoms occupy
the interstitial spaces.
Iron
Carbon
Stainless steel
(lll) Non Stoichiometric Defects
+ The defects in which the stoichiometry of the
compound ls changed are called non-
stoichiometric defects.
It arises when the ratio of the number of
atoms of one kind to that of the other kind or
the ratio of the number of cations to anions
becomes different than that indicated by the
chemical formula.
Solid State
Two types of non-stoichiometric defects :
(a) Metal deficiency defect
Possible only in case of compounds of
metals showing uariable oxidation states.
In case of some ionic crystals; positive
metal ions are missing from their original
lattice sites.
the presence of a cation of the same metal
with higher oxidation, state, then that of
the missing cation.
Example : In NiO [containing Ni2* and 02- ]
Ni2* ions are missing and hence a vacancy is
created. This vacancy is filled in by Ni3* iorls
thus creating a vacant site. The composition
of NiO, then becomes Ni6.gz Or.o.
Non-stoichiometric Nio.gz Or.o
(b) Metal excess defect
The two types of metal excess defects are :
(i) A neutral atom or a,n extra positiue ion,
occupies interstitial p osition.
Excess
neutral
Zn atom
@
@
@
@
@
@
@
@
NeutralZn atom at interstitial site
When ZnO is heated it decomposes as :
ZnO + Zn2* *10, +2e-
2L/
@
@
@
@
@
@
@
@@
@@
@@
@@
@
Vacancy
@
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?-, lt
Lln
+

11. MHT.CET
+ CHEMISTRY
The excess Zn2* ions are trapped in the
interstitial site. The electrons also occupy
interstitial positions .
In both cases, the non-stoichiometric
formula of ZnO ts Znlr + r) Or.o.
Anion uacan,cies (colour or F-centres)
be missing from its lattice site leavin g a
hole which is occupied by an electron.
Thus, the electrical neutrality is main-
tained.
The sites containing the electrons in the
anion vacancies are called F-centres as
they are resporlsible fo, imparting colour
to cr))stals (F-farbe meaning colour in
German).
For example, when NaCI is heated-in an
atmosphere of sodium vapour, the Cl -
ions diffuse to the surface where Na
atoms from the vapour are present. The
Na atoms ionise by losing electrons.
These electrons diffuse into the crystal
and occupy the vacant sites earlier
occupied by CI - ions.
The crystal of NaCI has excess Na. It
shows yellow colour due to the formation
of F-centre.
Non-stoichiometric formula of NaCl is
Nar+, Clr.o.
Solid State
ectrical Properties of Solids
Sotids are classified as conductors, insulators
and semiconductors based on their electrical
conductivity.
Conductors
(i) Electrical conductivity in the range of 104
to 107 Q-1 ,rr-1.
(ii) Metals conduct electricity with the help
of free electrons.
(iii)
}:T:T,li:n
conduct erectricitv bv move'
Insulators
(i) Solids having low electrical conductivity
in the range 10-
2o
to 10-
10
Q-1 *-1.
(ii) Ir{on-metals and molecular solids belong
to this category.
Semiconductors
(i) Solids having electrical conductivity in
the range 10-
6
to 104 Q-1 *-1.
(ii) Metalloids like silicon , germanium
belong to this category.
Band Theory
+ The interaction of energy leve1s of electrons
in the closely spaced constituent atoms in
solids results in the formation of bands.
+ A band is made up of closely spaced electronic
energy levels.
Band theory considers the formation of two
types of bands : con duction band and ualence
band.
Conduction band : The band formed from
empty or partially filled atomic orbitals of
higher energy is called conduction band. The
electrons in the conduction band are mobile
and delocalised over the entire solid.
Valence band : It is the band having lower
energy than the conduction band. The
electrons in this band are tightly bound to
the respective nuclei and hence are not free
to move.
Band gap : It is the energy difference
between the valence band and the conduction
band. Size of the band gap decides whether
the electron s from the ualence band can be
promoted to the conduction band.
@
EI
(ii)
An F-centre in a crystal
@
@
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@
:"
2*
ions and el itial sites
+
@
@
@@
ectrons at interst
@
@ Electron

12. MHT-CET + CHEMISTRY
If the band gap is too large and electrons
cannot be promoted to the conduction band
even after using thermal energy, then it is
called forbidden zorue.
If the band gap is small; the electrons from
the higher energy levels in the valence band
can, be promoted to the conduction band by
absorption of energy.
Electrical Properties Explained using Band
Theory
Metals
(i) In case of metals, the outermost electrons
occupy the conduction band. Since the
number of electrons is large, metals are good
conductors of electricity.
(ii) These conduction bands in metals can be
further labelled as 's' band, 'p' band etc.
depending on atomic orbitals involved in
band formation.
(iii) Band formation in metallic conductors results
in delocalisation of the outermost electrons
of all the meal atoms leaving behind metal
ions.
(iv) The metal cations of the crystal vibrate about
their mean positions. When temperature
increases there is an increase in vibrational
motion and thus the flow of electrons is
interrupted. Hence, conductiuity of metals
decreases utith an increase in temperature.
p-band
s-band
s-band overlapping bands
(a) (b)
Metalic conductor
lnsulators
(i) In this case, the valence band is completely
filled with electrons and the conduction band
is empty.
(ii) The band gap is very large and is called the
forbidden zor7e. Thermal energy is not
Solid State
sufficient to promote electrons from the
valence to the conduction band.
Empty conduction
band
Forbidden zorle
(Large energy gap)
Filled valence band
lnsu lators
Semiconductors
(a) Intrinsic Eemiconductors
(i) Electrical conductivity is intermediate
between metals and insulators.
(ii) The valence band is completely filled with
electrons and the conduction band is
empty. The energy gap between the va-
lence band and the conduction band is
smaller than in the case of an insulator.
(iii) Aboue absolute zero temperature; a few
electrons haue enough thermal energy to
cross ouer to the conduction band.
(iv) The conduction band becomes partially
filled and on application of electric po-
tential the semiconductor conducts a
small amount of electricity.
(v) Such pure semiconductors utith a low but
finite electrical conductiuity rs called ln-
trinsic semiconductor.
(vi) On increasing temperature; more elec-
trons gain energy and transfer from the
valence to the conduction band and hence
conductivity increases.
(vii) At higher temperature; the number of
electrons in the conduction band in-
creases and the number of vacancies in
the valence band decreases.
(viii) Semiconductors are insulators at low
temperatures and conductors at high
temperatures.
+
I

13. MHT.CET + CHEMISTRY
(b) Extrinsic semiconductors and dopirtg
(i) The process of adding a minute quantity
of an impurity to a semiconductor to
increase its conductiuity is called doping.
The added impurity is the dopant.
(ii) A semiconductor whose conductiuity has
been increased by dopirug is called an
extrinsic semiconductor s .
(iii) Extrinsic semiconductors may be n -type
or p-type.
(iv) n-type semiconductor is obtained by
adding a pentaualent i*purity from
group 15 to an intrinsic semiconductor
from group 14. The charge carriers are
electrons.
Examples ; Addition of phosphorus
(group 15) as an impurity to silicon (group
t4).
(v) p-type semiconductor are obtained by
doping a pure semiconductor material
with a triualent impurity from group 13.
Example : Addition of boron (group 13)
as an impurity to silicon (group 14).
In this case as the impurity atom has lesser
electrons an electron vacancy called o hole is
created. This hole has a tendency to accept
electrons from its vicinity and therefore
behaves like a positive charge. The charge
carriers are holes.
Magnetic Properties of Solids
(i) Electrons spin either clockwise or anticlock-
wise about their own axis.
Solid State
(ii) These spinning electrons behaue like tiny
magnels because their spinning generates a
magnetic field.
(iii) When the electrons are paired no magnetic
property is observed. However , Lt npaired
electrons exhibit magnetic properties.
(iv) Solids are classified as diamagnetic, para-
magnetic and ferromagnetic.
(v) Diamagnetic substa,nces .' They have all
electrons paired and are weakly repelled by
magnetic fields.
Pairing of electrons cancels their magn etic
moments.
Examples : Nz, F2, NaCI, H2O, Benzene.
(vi) Paramagnetic substances .' They have
unpaired electrons and are weakly attracted
by magnetic field.
The spinning of unpaired electrons reEults in
a magnetic moment.
These substances exhibit magnetism ONLY
in presence of external magnetic field and lose
their magnetism when the external magnetic
field is removed.
Examples : Oxygen, Cuz*, F"'*, Cr'*.
(vii) Feruomagnetic substances .' These sub-
stances contain large number of unpaired
electrons and are strongly attracted by mag-
netic field.
These substances retain their magnetism
even after the removal of the external mag-
netic field. They are permanent magnets.
Examples : Fe, Co, Ni, Gd, CrO2.
IMPORTANT FORMULAE
If edge length of a cube is o; mass of each
particle is m; l/6 is the Avogadro number; M ts
the molar mass; n is the number of particles per
unit ceII, then
-
1. Vo1ume of the cubic cell = o3.
2. Mass of unit ceII rs m x n.
3. Molar mass
= Mass of one particle
x Number of particles per mole
M- mX l/A
Density of the unit cell
Mass of unit cell
4.
mxn
p=
Volume of unit cell a3
nM
Density, p =;*
I For simple cubic cell, n - 1,
For body centred cubic ceII, h = 2,
For face centred cubic ceII, n = 4.)
b.

14. MHT-CET + CHEMISTRY
Packing efficiency and coordination number of cubic lattices
Solid State
Simple Cubic
Cell (SCC)
Body Centred
Cubic (BCC)
Face Centred
Cubic (rCC)
(i) No. of particles per unit cell
(ii) Radius of sphere
(iii) Volume of sphere
(iv) Total volume of particles
(v) Packing efficiency
(vi) Void space
(vii) Coordination number
(viii) Relation between edge length
and atomic radius
1
r- a
2
na3
6
no3
6
52.36 %
47 .64 %
6
a
2
2
J-s o
4
Jino'
16
Jino'
8
68%
32%
8
Ji"
4
CL
I_-
2J'
na3
.-
12J2
no3
.....,-
sJz
74%
26%
t2
-J-zo
4
Number of particles and unit cells in x g of
metallic crystal
Density, p =
No. of particles x M
Vo1ume of unit cell x Na
x
No. of unit cells in r g metal =
p o!
No. of unit cells in volume V of the metal
V
a3
Size and number of voids
(B is the atomic radius)
(i) Number of tetrahedral voids
= 2 x No. of atoms
(ii) Number of octahedral voids = No. of atoms
(iii) Size of tetrahedral void - 0 .225 R
(iv) Size of octahedral void - 0 .474 R
.+
where, M ts the molar mass and l/A
Avogadro number.
nM
.n=
P;,^t
No. of particles in
trNe
=
-=
M
=y
pa3
is the
x g of metal
xNt'xn
p a3 l/A
MULTIPLE GHOIGE OUESTIONS
, ,,,'G,herilctgri$ti*,...P*operties, : ::ltd,:: :, i,
Amorphous solids
(a) possess sharp melting points.
(b) possess long and short range order.
(c) have definite heat of fusion.
(d) show isotropy.
Which among the following show anisotropy?
Glass is ..
(a) a crystalline solid.
(b) true so1id.
(c) polymeric mixture.
(d) supercooled liquid.
An example of an amorphous solid is
(a) diamond
(b) glass
(c) plastic
(d) both (b) and (c)
3.
1.
2.
(a) plastics
(c) glass
(b) paper
(d) NaCl
4.

15. /
D.
MHT.CET + CHEMISTRY
The false statement is :
(a) Crystalline solids have sharp melting
points.
(b) Quart z LS crystalline SiO2.
(c) Glass is amorphous SiO2.
(d) Amorphous solids have a definite heat of
fusion.
Which of the followi.rg solids is isotropic?
(a) NaCl
(c) Pt
(b) Nio
(d) Rubber
The false statement is :
(a) Crystallites are the crystalline parts of
amorphous solids.
(b) NaF and MgO are isomorphs.
(c) Crystallites are also called unit cells.
(d) Atomic ratio is found to be the same in
case of isomorphic substances.
The correct statement is :
(a) Argonite and cristobalite are polymorphs
of CaCO3.
(b) cr-quartz and B-quartz are polymorphs of
silica.
(c) Graphite and diamond contain sp3 hybri-
dised carbon.
(d) Calcite is a form of calcium carbonate.
The ability of a given substance to assume
two or more crystalline structures is called
(a) anisotropy (b) polymorphism
(c) isomerism (d) isomorphism
10. Most crystals on cutting show a clean cleav-
age because, their atoms, ions or molecules
are
(a) weakly bonded together.
(b) strongly bonded together.
(c) spherically symmetrical.
(d) arranged in planes.
11. Compounds with identical crystal structure
and similar chemical formula are called
Solid State
'i , :,C:rystalline Solids
12. The incorrect match is :
(a) Metallic solid -+ Go1d.
(b) Ionic solid + CaF 2.
(c) Network solid + Quartz.
(d) Polar molecular solid + Dry ice.
13. Which of the following is an example of polar
molecular solids?
(a) Ice
(c) SOz
L4. A crystalline solid of neon ..
(a) is an example of polar molecular solid.
(b) is an example of a network solid.
(c) does not exist.
(d) shows the presence of London forces
between the constituent atoms.
15. Solid COz is an example of ... solid.
(a) ionic (b) molecular
(c) covalent (d) metallic
16. Solid NaCl is a bad conductor of electricity
because .
(a) it does not contain any ions.
(b) it is a non-polar compound.
(c) the ions of Na* and Cl - are not free to
move.
(d) it does not contain mobile electrons.
17 . F or a network solid; the constituent particles
are
(a) unbonded atoms.
(b) polar molecules.
(c) covalently bonded atoms.
(d) cations and anions.
18. Iodine exists as .
(a) polar molecular solid.
(b) ionic solid.
(c) non-polar molecular solid.
(d) hydrogen bonded molecular solid.
19. Diamond is an example of .
(a) ionic crystal
(c) covalent solid
(b) ionic solid
(d) amorphous solid
6.
F'
l.
(b) Dry ice
(d) Iz
8.
9.
(a) isomorphs
(c) isomers
(b) polymorphs
(d) isostructures

16. MHT.CET + CHEMISTRY
20. The incorrect statement about ionic solids
is:
(a) Constituent particles are held together by
coulombic force.
(b) They are good conductors of electricity in
the solid state.
(c) They are brittle.
(d) They have high boiling points.
21. The coruect statement regarding molecular
solids is :
(a) They have weak intermolecular forces.
(b) They are insulators.
(c) They are hard solids.
(d) Both (a) and (b).
22. The incorrect pair is :
(a) SiOz -+ Network solid
(b) Carborandum + Network solid
(c) Graphite + Insulator
(d) NHq i Hydrogen bonded molecular solid
23. F or metallic solid of sodium the particles
which occupy the lattice points are
(a) molecules
(c) protons
(b) metal ions
(d) atoms
24. The interparticle forces in solid hydrogen are
(a) covalent bonds.
(b) van der Waal's forces.
(c) dipole-induced dipole interaction.
(d) ionic bonds.
25. Which of the following is a polar molecular
solid?
(a) COz 0) SOz (c) Iz
(d) Diamond
(a) ionic bond (b) covalent bond
(c) dipole-dipole attraction
(d) dipole-induced dipole interaction
27. Graphite is a good conductor of electricity
while diamond is an insulator even though
they are polymorphs of the same element
because .
(a) intermolecular forces are stronger in
diamond.
(b) diamond is a covalent crystal.
Solid State
(c) graphite has delocalised Pi electrons
while diamond does not.
(d) weak van den Waal's forces exist in graph-
ite.
A solid melts slightly above 0 oC
and is a poor
conductor of electricity. Hence, it may be
a ........
(a) ionic solid
(c) covalent solid
29.
29. Which of the following is not a soft solid?
(a) Sodium
(c) Phosphorus
(a) silica
(c) silicon
(b) network solid
(d) molecular solid
(b) Copper
(d) Polonium
(b) sodium silicate
(d) silicon carbide
30. The major binding force in Buckminster
fullerene is
(a) ionic bond (b) covalent bond
(c) coordinate bond (d) metallic bond
31. Which statement is not correct about
fullerene C66?
(a) It contains twenty six membered rings
' and 12 fle membered rings.
(b) AII carbon atoms undergo sp2 hybridi-
sation.
(c) A six membered ring is fused with six
membered rings on1y.
t'*iffi"LTH;*,;:'is rused with six
32. Quartz LS a crystalline variety of
Crystal Systems and Unit Gells; Packing
in One, Two and Three Dimensions
33. The packing fraction for a body centred cube
is ..
(a) 68% (b) 0.52 (c) 0.68 (d) 0.42
34. There are a total of types of Bravais
lattices.
(a) 12 (b) t4 (c) 10 (d) 6
35. A primitive unit cell has particles present
at.
(a) the corners and the body centre.
(b) only at the corners of the unit cell.
(c) at the face centres and the body centre.
(d) at the corners and at the edge centres.

17. MHT-CET
+ CHEMISTRY
86. An ionic compound crystallines in F CC type
structure with 'A' ions at the centre of each
face and 'B' ions occupying corners of the
cube. The formula of the compound is ..
(a) ABa ft) A3B (c) AB (d) ABB
g7. The number of atoms in 50 g of FCC crystal
with density 10 glcc and cell edge equal to
200 pm is equal to
(a) 12 x 1023 atoms (b) 25 x 1023 atoms
(c) 12 atoms (d) 6 x lO24 atoms
88. The interionic distance for cesium chloride
crystal will be .
r
(a) a &)
Jl" @ + (d) oJi
2Js
39. An element (atomic mass 2OO g mol -1)
crystallises in a simple cubic structure. If the
density of the unit cell is 7 g cffi- 3,
what is
the radius of an atom of the element?
(a) 4.76 x 10- 8
.* (b) 1.812 x 10- 5
.-
(c) 4.76 x 10-'3 .* (d) 1.812 x 10- 8
.*
40. The number of tetrahedral sites per sphere
in FCC structure is ..
(a) 1 (b) 2 (c) 3 (d) 4
4L. The number of atoms in a body centred cubic
unit cell are
(a) 1 (b) 2 (c) 3 (d) 4
42. The correct sequence of layers in cubic close
packing (CCP) is ..
(a) AB AB AB .... (b) AAAAA....
(c) ABC ABC .... (d) AB AA AB AA ....
43. The more efficient mode of packing of
identical atoms in one layer is ..
(a) square close packing pattern.
(b) hexagonal close packittg pattern.
(c) cubic close packing pattern.
(d) simple cubic pattern.
44. The empty space in hexagonal close packed
structure is about .
(a)32% (b)34% (c)74% (d)26%
45. A certain ionic compound BA crystallises in
a cubic lattice in which both B* and A- have
a coordination number of 8. Hence, the type
of unit cell is ..
(a) simple cubic
(b) body centred cubic
Solid State
(c) face centred cubic
(d) hexagonal close packed
46. The cubic unit cell of metal (molar mass
27 S mo1 -1; has an edge length of 400 pm. Its
density is 2.7 g .rrr- 3. The cubic unit cell
is ..
(a) FCC (b) BCC
(c) SCC (d) primitive
47 . Copper crystallises in a face centred cubic
lattice with a unit ceIl edge length of 361 pm.
What is the radius of the copper atom in pm?
(a) 757 (b) 181 (c) 108 (d) t28
48. Tota1 number of voids in 0.5 mole of a
compound forming hexagonal close packed
structure are
(a) 6 x 1023
(c) 9 x 1023
(b) 3 x 1023
(d) 4.5 x 1023
49. The number of unit cells in 4 g of X (atomic
mass 40 g mol -t) *hich crystallises in BCC
(l/a = Avogadro number)
(b) 2x 0.1NA
(d) 2 A/A
50. A solid is formed by two elements P and Q.
The element Q forms cubic close packing and
atoms of P occupy one-third of tetrahedral
voids. The formula of the compound is ..
(a) PQs ft) PgQ (c) PzQs (d) PaQz
51. The false statement is :
(a) A lattice is a geometrical arrangement of
points in a three dimensional aruay.
(b) The constituent particles attached to the
lattice point form the basis of the space
lattice.
(c) Geometric shape of the unit cell and the
macroscopic crystal is the same.
(d) The primitive unit ceII is same as the FCC
type of unit cell.
52. The correct statement from the ones given :
(a) a constituent particle at the edge of the
unit cell contributes U 4t}, to the unit cell.
(b) the greater the coordination number
greater is the void space in the crystal.
(c) a crystal plane is a one dimensional close
packed structure.
pattern is
(a) 0.1 l/A
0.11/^
(c)
,a

18. MHT.CET + CHEMISTRY
(d) an octahedral void is surrounded by eight
spheres.
53. A body centred cubic lattice has a coordina-
tion number and number of atoms per unit
cell respectively
(a) 4,2 (b) 6, 2 (c) 8, 2 (d) 2, 8
54. The least packed cubic system is and
its percentage of void space is ..
Solid State
61. If a compound is formed by X, Y and Z atoms
with Z at the corners, Y is present at LlZ of
the tetrahedral voids and X is present at Il2
of the octahedral voids which of the followi^g
is the molecular formula of the compound?
55. An ABC ABC type arrangement of constitu-
ent particles leads to the formation of a
close packed system.
62. The mass of a face centred cubic cell is
64 x 10- " g.The atomic mass of the metal
is ..
(a) e6 (b) 32 (c) 48 (d) 16
63. A certain element having atomic radius of
0.84 Ao crystallises in fcc structure. The edge
Iength of the crystal would be
(a) 2.375 cm (b) 2.375 x 10- 8
..r,
(c) 2.375 x 10-10 cm (d) 2 .375 x 10- 8
*
64. Silver crystallises in F CC structure. If atomic
mass of Ag is 108 g mol -1; the mass of a unit
cell of Ag is ..
(a) 7.2 x 10- 'u g (b) 7.2 x 10-'u g
(c) 72 x 10-'o g (d) 7.2 x 10-'u kg
65. An element crystallises in bcc structure. If
the atomic radius is 120 pm. The edge length
of the unit cell is ..
(a) SCC, 52 Yo
(c) BCC,32 o
(a) hexagonal
(c) cubic
(b) scc, 48 oh
(d) BCC,,68 %
(b) square
(d) tetragonal
(a) XYzZz
(c) XzY 4Z
(a) 120 pm
(c) 339 pm
(a) 16.6 x ro24
(c) 16.6 x lO-24
(b) Xz zY
(d) xYZ4
(b) 277 pm
(d) 135 pm
(b) 6 x 1023
(d) 16 x 1018
56. The incorrect statement is :
(a) Both octahedral and tetrahedral voids are
present in CCP arrangement.
(b) Packing fraction =
Packing efficiency
100
(c) The tetrahedral void is surrounded by
four spheres.
(d) The coordination number for one dimen-
sional packing is 4.
57. Suppose the mass of a single Ag atom is 'm'.
If Ag metal crystallises in FCC lattice with
unit cell of length'e', the density of Ag metal
is ..
r")4 b)ry k)4 (d) L
A,
'-'l
A'
-,
A'
/
4A3
66. A particular ionic solid BA crystallises in FCC
structure. The anions occupy all corners and
face centres while the cations occupy half the
tetrahedral voids. Hence, the number of BA
molecules present in 2 unit cells will be .
(a) 4 (b) 8 (c) 3 (d) 2
58. The number of tetrahedral
cell of a face centred cubic
atoms is ........
(a) 4 (b) 6 (c) 8
59. In a compound atoms of Y form ccp lattice
and those of element X occupy 213'd of the
tetrahedral voids. The formula of the com-
pound will be .
(a) X2Y3
(c) XgYn
60. Total volume of atoms present in face centred
cubic unit cell of a metal is (r is the
67 . The number of atoms present in 50 g of BCC
crystal having edge length 100 pm would
be. .(p-6gcm-3)
voids in the unit
Iattice of similar
(d) 10
atomic radius)
20a
(a)
-
IT r"
/3
12a
(c)
T
7rr"
(b) x3Y
(d) x4Y3
b)+n,3
(o
+ n,3
68. In a cubic lattice of ABC, A atoms are present
at all corners except one corner, which is
occupied by C atom. B atoms are present at
the face centres. Hence, the formula of the
compound is ..
(a) ABTC (b) AzBz+C
(c) AB7C24 (d) AzBCz+
69. How many atoms are present in a cubic unit
ceII having one atom at each corner and face

19. MHT-CET
+ CHEMISTRY
centre of the unit cell and two atoms on
body diagonal of the cell?
(a) 8 (b) 6 (c) t2 (d) 4
70. How many ce1ls are present in a cube shaped
ideal crystal of NaCI of mass 1.0 g? (Atomic
mass : Na = 23, Cl = 35.5)
(a) 2.5 x lO21 unit cells.
(b) 5.1 x lO21 unit cells.
(c) 1.28 x tO21 unit cells.
(d) 1.7 x 1021 unit cells.
71. The number of NaCl molecules in a unit cell
of its crystal is
(a) 2 (b) 4 (c) 6 (d) 8
72. How many CI - ions are there around Na*
ion in NaCl crystal?
(a) 3 (b) 4 (c) 6 (d) 8
73. A certain metal crystallises in a BCC lattice
with an edge length of 6 Ao. The distance
between the nearest neighbours in the
structure wiII be .
(a) 5.196 A" (b) slE a"
(c) .E a' (d) both (a) and (b)
7 4. A certain metal crystallises in a SCC lattice.
If the edge length of the unit cell is 350 pm
thq atomic radius of metal atom will be .
Solid State
cubic unit cell. If all the face centre atoms
along one axes are removed, then the
resultant stoichiometry of the solid is ..
(a) AB2 ft) A2B (c) A+Bs (d) A3B4
Radius of an octahedral void relative to the
radius of the atom in a close packed structure
is ..
(a) t.4t4 (b) 0.4t4 (c) 0.225 (d) r.225
80. The correct order of packing efficiency for
different types of unit cells is ........
(a) fcc < bcc ( scc (b) bcc > fcc ) scc
(c) fcc > bcc ) scc (d) scc < bcc > fcc
81. Edge length of a cube is 400 pm. Its body
diagonal will be .
@
each
79.
7 5. Each face of a cubic unit cell is in contact with
how many unit ce1ls?
(a) 1 (b) 2 (c) 4 (d) 6
76. The most efficient mode of packing of identi-
cal atoms in two dimensions is ..
(a) square close packing.
(b) hexagonal close packing.
(c) cubic close packing.
(d) both (a) and (b).
77. Total volume of atoms present in a body
centred cubic ceII of a metal is .. (r is the
atomic radius)
20a24a
tu) * rrr't &) S rrr'
33
, 72 16 3
(c) Inr (d)
-nr-
33
78. A solid AB has NaCI structure atoms of a
occupy the corners and face centres of the
82. If 'a'is the length of the side of the cube; the
distance between the body centred atom and
one corner atom of the cube will be .
n h" (d)
#"
83. Lithium has a BCC structure. The edge
length of the unit cell of lithium metal with
density 5.0 kg m- 3
and an atomic mass of
6.9 g mol -1 is .. (l/a = 6 x lO23 mo1 -1)
(a) t54 pm (b) 352 pm
(c) 527 pm (d) 284 pm
84. The ratio of Fe3
* and Fe2
* ions in Fes.g S,..0
is ..
(a) 4 (b) 0.5 (c) 2 (d) 0.28
85. If the edge length of a BA unit cell is 500 pm.
What is the bond length of B-A bond if it
crystallises in the F CC structure?
(a) 151.3 pm
(c) 300 pm
(b) t75 pm
(d) 240 pm
(a) 600 pm
(c) 692.8 pm
(a) 200 pm
(c) 500 pm
(b) t.732 pm
(d) t42 pm
(b) 250 pm
(d) 300 pm
(b) AzBOz
(d) AB zOz
o>f' @+'
86. Structure of a mixed oxide is cubic close
packed (CCP). The cubic unit cell is composed
of oxide ions. One fourth of the tetrahedral
voids are occupied by a divalent metal A and
the octahedral voids are occupied by a
monovalent metal B. The formula of the oxide
is ..
(a) ABO2
(c) A2B3O4

20. MHT.CET + CHEMISTRY
87 . The edge length of a face centred cubic cell is
508 pm. If the radius of the cation is 110 pm,
the radius of the anion is ..
Solid State
fraction of tetrahedral holes occupied by
magnesium ions; m and n respectively
are
rut1,+ ft)1, 1 (c)1, 1 (d)1, 1
2'8 / -) 4
/ 2' 2 -/ 4'g
, ,,,r,Gry$tal .Ddfects and knpeffiCtliO:ns
97. If NaCI is doped with 10- 4 mol percent of
SrCI2, the concentration of cation vacancies
will be . . (l/a = 6 x 1023 mo1-1)
(a) 6 x 1014 mol -1 (b) 6 x 1015 mo1 -1
(c) 6 x 1016 mol -1 (d) 6 x 1017 mol -1
98. Schottky defect occurs mainly in electrova-
lent compounds where ........
(a) positive and negative ions are of different
size.
(b) positive and negative ions are of same
size.
(c) positive ions are small and negative ions
are big"
(d) positive ions are big and negative ions are
small.
Which of the following compounds shows both
Frenkel and Schottky defects?
(a) NaCl (b) AgCl (c) AgBr (d) KCI
100. The crystal with metal deficiency defect is ...
(a) NaCI (b) KCI (c) FeO (d) ZnO
101. Stoichiometric defects are known as thermo-
dynamic defects because
(a) they affect thermodynamic stability of the
solid.
(b) they may be formed by absorption of heat
by the so1id.
(c) they are dependent on the thermody-
namic properties of the solid.
(d) both (a) and (c).
L02. The ionic solid which shows both Frenkel as
well as Schottky defect is ..
(a) AgBr (b) KCI (c) NaCl (d) CsCI
103. F-centres in ionic crystals are
(a) lattice site containing electrons.
(b) interstitial sites containing electrons.
(c) lattice sites which are vacant.
(d) interstitial sites which absorb radiation.
88. A metal crystallises with a face centred cubic
lattice. The edge of the unit cell is 408 pm.
The diameter of the metal atom is ..
(a) 285 pm
(c) L44 pm
(a) 288 pm
(c) L44 pm
(b) 3e8 pm
(d) 618 pm
(b) 408 pm
(d) 204 pm
89. In the crystal of which one of the followi.tg
ionic compounds would you expect maximum
distance between the centres of cations and
anions?
(a) CsI (b) CsF (c) LiF (d) LiI
90. In a particular crystal 'A' atoms are present
at all the corners while 'B' atoms are placed
at every face centre. The formula of the
compound is ........
(a) AB (b) ABB (c) AzBz (d) AzB3
91. A void surrounded by 6 spheres out of which
three spheres are above and three spheres
are below is called . 99.
(a) cubic void (b) tetrahedral void
(c) octahedral void (d) triangular void
92. The mass of a unit cell of a body centred cubic
crystal of a metal is 18 x 10- " g. The atomic
mass of the metal is ..
(a) 54 (b) 18 (c) 26 (d) 34
93. Which of the followirg compounds has the
highest lattice energy?
(a) LiBr (b) LiCl (c) LiI (d) LiF
94. How many atoms are present in a cubic unit
ceII having one atom at each corner of the
cell and 2 atoms at each body diagonal?
(a) 5 (b) 6 (c) 8 (d) 4
95. The number of unit cells in 1 mole of potas-
sium chloride is
(Atomic mass : K = 39, CI = 35.5)
(a) 1.b x 1023 G) 6 x 1023
(c) 0.5 x to24 (d) 6 x 1o2o
96. If a unit ceII of a mineral has CCP array of
oxygen atoms with m fraction of octahedral
holes occupied by aluminium ions and n
I
t

21. MHT-CET + CHEMISTRY
105.
106.
107.
109.
109.
1 10.
The false statement among the following is :
(a) The faster the crystallisation of the solid
the greater the defects created.
(b) Defects may be point, line or plane defects.
(c) Defects modify the properties of crystals.
(d) Schottky defect is found in compounds
where cations and anions have large
difference in size.
The true statement is :
(a) Frenkel defect is observed in KCl.
(b) Frenkel defect is a combination of vacancy
defect and interstitial defect.
(c) Metal deficiency defect is a stoichiometric
defect.
(d) Electrical neutrality is not maintained in
crystals showing non-stoichiometric
defects.
Which defect causes a decrease in the density
of the crystal?
(a) Frenkel (b) Schottky
(c) Interstitial (d) Both (a) and (c)
White ZnO turns yellow on heating because
of ........
(a) Frenkel defect
(b) metal excess defect
(c) metal deficiency defect
(d) Schottky defect
The flame colours of metal ions are due to ....
(a) Frenkel defect (b) Schottky defect
(c) metal deficiency defect
(d) metal excess defect
When electrons are trapped into a crystal in
anion vacancy; the defect is known as ........
(a) Schottky defect (b) Frenkel defect
(c) Stoichiometric defect
(d) F'-centres
Experimentally it was found that a metal
oxide has formula Ms.gsO. Metal'M'present
as M2
*
and M3
*
in its oxide. Fraction of the
metal which exists as Ms
*
*orld be
(a) 7.0t %
(c) 6.0 5 %
(b) 4.08 %
(d) 5.08 Yo
Solid State
Which of the following defects is seen in FeO?
111.
(a) metal excess
(c) impurity
(b) metal deficiency
(d) displacement
L1,2. When NaCl crystal is doped with CaCl2 the
type of defect produced will be .
(a) Interstitial
(c) F renkel
(b) Schottky
(d) Impurity defect
113. The false statement about NaCI is :
(a) The crystal of NaCl shows anion vacancy
defect.
(b) F-centre defect is cation vacancy defect.
(c) NaCl has a yellow colour due to colour
centres.
(d) NaCl shows non-stoichiometric defect.
Ll4. A certain metal oxide AO has a few ions of
A'* being replaced by ions of A3* having
higher oxidation state. Hence, in case of this
crystat ........
(a) there is the presence of metal deficiency
defect.
(b) the crystal develops a negative charge.
(c) for every 3 ions of A'* removed two ions
of A3* are added.
(d) both (a) and (c).
115. The false statement is :
(a) Solid solutions show impurity defect.
(b) Stainless steel is an example of interstitial
impurity defect.
(c) In case of brass Zn ts the host and Cu is
the foreign atom.
(d) An aliovalent ion can be used to introduce
an impurity defect.
116. The true statement from the following is :
(a) Schottky defect is called a pair defect.
(b) A crystal showing interstitial defect
always shows a decrease in the density.
(c) Schottky defect is shown by compounds
having low ionic character.
(d) Frenkel defect is shown in compounds
where ions have high coordination
number.
L1-7 .In a solid ionic lattice a cation leaves a lattice
site and occupies an interstitial site. This
defect i-s ........

22. MHT-CET + GHEMISTRY
(a) Schottky defect (b) Frenkel defect
(c) metal deficiency defect
(d) metal excess defect
118. Which of the following defects is also known
as dislocation defect?
Solid State
(b) Extrinsic semiconductors are formed by
adding an impurity.
(c) The band gap can be crossed easily by the
electrons on supplying energy.
(d) AI1 the above.
L26. A silicon solar battery is ..
(a) n-type semiconductor.
(b) p-type semiconductor.
(c) combination of n and p-type semiconduc-
tor.
(d) used only at high temperatures.
Magnetic Properties
127. The diamagnetic substance from the follow-
ing is ..
(a) F e (b) HzO (c) Cu2* (d) CrO2
128. The ferromagnetic substance is ..
119. On doping germanium with a small amount
of gallium a type semiconductor is
obtained.
(a) F renkel
(c) Impurity
(a) n-type
(c) intrinsic
(a) Boron
(c) Phosphorus
(b) Schottky
(d) Metal deficiency
(b) p-type
(d) both (a) and (c)
(b) Carbon
(d) Arsenic
120. The true statement is :
(a) Metalloids are usually insulators above
room temperature.
(b) The size of the band gap decides the
electrical conductivity of a substance.
(c) Semiconductor prepared by adding a
dopant are called intrinsic semiconductor.
(d) Electrolytes use free electrons to conduct
electricity.
LZL Which of the following dopants would give a
p-type semiconductor with silicon?
129. The false statement is :
(a) Paramagnetic substances have unpaired
electrons.
(b) Paramagnetic substances can be magne-
tised permanently.
(c) Diamagnetic substances have all elec-
trons paired.
(d) Both (b) and (c).
(a) Gd
(c) N2
(b) benzene
(d) NaCl
122. A semiconductor of silicon can be made lB0. CrO2 is ........
n-typebyadding........ ,,; ,. A r:
(a) arsenic (b) a pentavalent impurity ja]
:iamacneti:
@) paramagnetic
(c) aluminium (d) both (a) and a,
--.---' (c) ferromagnetic
(d) a substance with no magnetic moment.
123. To get a p-type semiconductor the impuritv
added to si should have the following;;;; 131' The diamagnetic species among the following
of valence electrons ........ are """"
(a) 4 (b) 3 (c) 5 (d) 1 (a) sc3* (b) Fe3
* (") c2HsoH
r24. Band theory explains ........ (d) both (a) and (c)
(a) the difference between valence and con- 132' The magnetic moment of a substance depends
duction bonds. on """"
(b) electrical conductivity of metals. (a) the number of unpaired electrons'
(c) valencies of metals. G) the total number of electrons'
l
(d) physical properties of metals. (c) the presence of an external magnetic field'
I
125. which of the following statements is true (d) both (a) and (c)' I
i
about semiconductors? 133. Ferromagnetic materials are those, which.....
(a) Intrinsic semiconductors become conduc- (a) have large number of unpaired electrons'
tors when temperature is increased.
I

23. MHT-CET + CHEMISTRY
are strongly attracted by an
magnetic field.
are permanent magnets.
all the above.
case of diamagnetic substances ........
there are no unpaired electrons.
the number of electrons having clockwise
and anticlockwise spin is the same.
Solid State
(c) they are weakly repelled by an external
magnetic field.
(d) all the above.
Which arrangement of electrons describes
ferromagnetism?
(a)ttJJ ft)tttJJ
(c) ttttt (d)tJtJ
@
external
(b)
(c)
(d)
L34. In
(a)
(b)
1 35.
ANSWERS
1. (d)
6. (d)
1 1. (a)
16. (c)
21. (d)
26. (b)
31. (c)
36. (d)
41. (b)
46. (a)
51. (d)
56. (d)
61. (a)
66. (b)
2. (d)
7. (c)
12. (d)
17. (c)
22. (c)
27. (c)
32. (a)
37; (b)
42. (c)
47. (d)
52. (a)
57. (a)
62. (a)
67. (a)
3. (d)
8. (b)
13. (c)
18. (c)
23. (b)
28. (d)
33. (c)
38. (b)
43. (b)
48. (c)
53. (c)
58. (c)
63. (b)
69. (b)
4. (d)
9. (b)
14. (d)
19. (c)
24. (b)
29. (b)
34. (b)
39. (d)
44. (d)
49. (c)
54. (b)
59. (d)
64. (c)
69. (c)
5. (d)
10. (d)
15. (b)
20. (b)
25. (b)
30. (b)
35. (b)
40. (b)
45. (b)
50. (c)
--l
b b. (c)
60. (d)
65. (b)
70. (a)
71. (b)
76. (b)
81. (c)
96. (d)
91. (c)
96. (a)
10 1. (b)
106. (b)
111. (b)
1 16. (a)
1-z1. (a)
126. (c)
131.(d)
7 2. (c)
77. (b)
92. (b)
87. (c)
92. (a)
97. (d)
L02. (a)
107. (b)
rtz.(d)
117. (b)
L22.(d)
127. (b)
t32.(d)
73. (d)
78. (d)
83. (d)
88. (a)
93. (d)
98. (b)
103. (a)
108. (d)
113. (b)
1 18. (a)
123. (b)
128. (a)
133. (d)
7 4. (b)
79. (b)
94. (d)
89. (a)
94. (c)
99. (c)
104. (d)
109. (d)
LL4. (d)
119. (b)
124. (b)
129. (b)
134.(d)
75. (a)
80. (c)
95. (b)
go. (b)
95. (a)
100. (c)
105. (b)
110. (b)
1 15. (c)
120. (b)
L25. (d)
130. (c)
13 5. (c)
HINTS AND SOLUTIONS
2. Since NaCl is a crystalline solid it is aniso-
tropic.
3. Glass is an amorphous solid (pseudo solid)
and behaves like a supercooled liquid of high
viscosity.
5. Amorphous solids melt over a range of
temperature.
7. Crystallites are the crystalline parts of an
amorphous solid.
13. The C - O bond is polar however the resultant
dipole moment in COz is zero.
O=C=O
.e* *+
14. Neon in the solid state is composed of
unbonded Ne atoms held together by London
forces.
15. Lattice points are occupied by molecules.
16. NaCI is an electrolyte in the fused or aqueous
state as ions (charge carriers) are free to
move.
22. Carborandum is silicon carbide (SiC).
24. Since Hz is a non-polar molecule the inter-
molecular forces of attraction are weak Van
der Wall's forces.
26. Fullerene (Coo) contains 60 carbon atoms held
together by covalent bonds.

24. MHT-cET+cHEMtsrRY @
27. Diamond contains sp3 hybridised carbon
while graphite has sp2 hybridised carbon
atoms.
28. Molecular solids have low melting point and
do not contain free electrons or free ions to
caruy current.
29. Copper is a metallic solid with FCC arrange-
ment while Na and Po have BCC and SCC
arrangements respectively Phosphorus is a
molecular solid.
30. Buckminster fullerene is Coo.
31. A six membered ring is fused with a five or
six membered ring.
34. A total of 7 crystal systems with 14 different
types of unit cells in total.
36. 'B' atoms at the corners of the cube.
.'. No.of Batoms-8"'-1
8
'A' atoms at the face centres of the cube each
face centre atom contributes Llz.
No. of 'A'atom = g * I
- B.
2
Formula of the compound is AB3.
37. For FCC;
Solid State
o3 = 4.76 x 10-'3 .-'
a = 3.62x 10-8.*
r = I = 1.812x 10-8.*.
2
42. hcp .... AB AB .... arrangement.
ccp .... ABC ABC arrangement.
43. AB AB type arrangement in two dimensions.
The spheres of the second layer are placed
betwe en 2 spheres of the first layer.
nM
46.
a
47.
d=
2.7 =
n=
= 3.84
Unit cell is
l/A . a3
6x1023x(4x10-8)3
2.7 x 64x 10-24 x 6 x 1023
[400pm - 4x 10-8cm]
n (27)
x l/a I atoms.
)
t in one unit ceII.
are present in Io:lr^
I
( ,-)
27
A
-+
F'CC type.
361
=-- = 127.6pm.
2x 1.414
Density =
.'. 10 =
.'. fu[ =
2J'
48. F or N close packed spheres, the number of
tetrahedral voids is '2IV' an the number of
octahedral voids is '.4/'.
Number of ions in 0.5 mol of the compound
=0.5x6x1023=3x1023
.'. Number of tetrahedral voids
= 2(Bx 1023)=6x1023
Number of octahedral voids = 3 x 1023
Total number of voids = 9 x 1023.
4M
u3 l/a
4xM
(2x10-8)3x6x1023
10x8x10-24x6x1023
l/A
4
49. 49 = 40
mol
2 atoms are
=12
L2 g contain
contain
50x6x1023
4
6 x 1023 atoms 50 g wilt
- 25 x 1023 atoms.
L2
38. Since CsCI is a BCC unit cell with Cs* at the
body centre position and Cl - at the corners
of the unit cell.
Distance between Cs* and Cl -.
1
=, xBodYdiagonal
=
1*.E a-Ji o
22
39. For SCC;
M
.'. 0.1 l/A atoms
unit cells.
50. Atoms of Q are in ccp arrangement. F or every
atom of Q there are 2 tetrahedral voids.
Atoms of P occupy (1/3)'d of these voids.
Number of voids occupied - 2t + = ?.
33
RatioofP and a = : : l=2:3. PzQg.
J
51. The primitive unit cell is same as the simple
cubic cell.
52. Greater the coordination number more com-
pact is the packing and lesser the void space.
(4
-t_
.40
presen
d=
l-
D
au
200
6x 1023 xoB

25. MHT.CET + CHEMISTRY
Crystal planes are two dimensional. An
octahedral void is surrounded by 6 spheres.
56. The coordination number for one dimensional
packing is 2 (single layer of atoms).
4MM
Solid State
57. d-
an
Na o' l/A
element in this
65.
a=
66. The solid
A- ions :
Je
"
v
t-
4
4xL20
t.732
contains
1
x8
8
(corners)
- 277 .l pm
B* and A- ions.
1
+ x6 = 4
2
(face centres)
is the mass of one atom of
case it is 'm'.
3
r
Z
Corners
4m
A = ., .
au
58. Since FCC unit ceII contains 4 atoms. No. of
tetrahedral voids is 2 x 4 = $.
59. No. of tetrahedral voids
24
No. of X atoms - 2 x -
33
Ratio of X : :l=4:3.
43
60. Volume of one atom = = fi r
3
Volume of 4 atoms (since F CC has
atoms per unit ceII)
Tetrahedral voids - 8
B* ion, =
;
x 8 (tetrahedral voids)
1 unit cell contains 48* and 4X ions.
Orre unit cell contains four BA molecules.
In 2 unit cells + 8 molecules of BA.
2M
67. For BCC, d - l/A . a3
2x50
No. of atoms x (1 x 10-8)3
of atoms in 50 g of crystal
= 'oo - - 16.6 x ro24 atoms
6 x 10-'*
68. A atoms present at 7 corners.
.'. ContributionofA- 7x7 -7
88
C atom present at one corner.
Contributes I
8'
B atoms at the face centres.
.'. ContributesOrl-3.
2
4
Y--3 6-
No.
4q16
= 4X-nfu= IT
33
61.XY
octahedral Tetrahedral
voids voids
1:2:
11
1x- : 2x
22
1
:1
2
.'. Ratio ofX : Y : Z - 1 : 2 : 2.
.'. Formula = XY 222.
62. 4 atoms have a mass of 64 x 10- " g.
6 x 1023 atoms have a mass of
6x1023x64x10-23
4
= 96 S mol-l
63. r=+
2J2
.'. a = 0.84 x2x1.414-2.375 A"
a = 2.375 x 10-10 m
= 2.375 x 10-8 .*.
64. FCC unit cell contains 4 atoms.
6 x 1023 atoms of Ag weigh 108 g.
.'. 4 atoms of Ag weigh 72 x 10- " g.
Ratio of A: B : C -
Formula is A7R14C.
69. Each corner atom contributes
face centre atom contribut
1
,"r,
No. of atom, = 1 x 8 * f x 6 - 4.
82
There are four body diagonals.
Total No. of atoms on body diagonals
= 2x4=8
.'. Total No. of atoms per unit cell
= 4+8=12.
1
70. lgNaCl = 5gS mol
7 D.1
d
88 =
1
8
7:24:1
and each

26. MHT.CET + CHEMISTRY
1
1 g NaCl = rr" x 6 x 1023 molecules
4 molecules of NaCI are present in one unit
ceII t '.' it shows F CC arrangement.]
#
x 6 x 1023 molecules are present in
' 2.56 x lO21 unit cells.
72. In NaCI, each CI - ion is surround.ed by 6 Na+
ions and each Na* is surrounded by six Cl -
ions. Hence, CN of both ions is 6.
7 3. BCC lattice.
.'. Distance between nearest neighbours
_ Ji o
- .6 * 6
-
22
7 4. For simple cubic system,
a 350
g.EA"
r = 2= Z =I75pm
77 . Volume of 1 sphere = +" 13 .
3
Since BCC lattice has 2 spheres per irnit ceII.
Totalvolume - 2xlnrn =
8
n13.
33
78. There were 6 atoms of A at face centres. If
the face centred atoms along one of the axes
is removed, then 2 atoms of A are removed.
No. of A atoms per unit cell
11
= 8x- + 4x- -3
82
(corners) (face centred)
No. of B atoms per unit cell
= Dx! + 1 -,1
(edge centres) (bodY centre)
Hence, the resultant stoichiometry is AsBn.
[NaCl structure .'. B occupies the voids at
the edge centres and at the body centre.]
81. Body diagonal is Jg
".
= 1.732 x 400 = 692.8 pm
83. For BCC,
2M
Solid State
F e1o.g) S(r.o)
Let the number of F e2* be r.
The number of Fe3* be (0.9 - r)
2x+3(0.9-x)+(-2)-0
2x+2.7-3x-2-0
.'. x - 0.7.
Number of F e2* = 0.7
Number of Fe3* = 0.2
Ratio of
Fe3* 0.2
0.28.
Fe2* 0.7
85. 2(r*+r-)=o 2(r*+r_)=500
r**r_ = 250.
86. 02* : ,L2* : B*
(ccp (occupies (occupies
arrange- tetrahedral octahedral
ment) voids) voids)
1
1 : 2"2 : lx1
1
1 , i : l=2:1:2.
.'. Formula of the compound is AB2Oz.
87. 2 (r*+ r-) = a .'. 2 (110 + r--)=508
r_ = 144 pm.
88. r- o:
2J'
Diameter = 2r =
J, 1.414
- 288 pm
89. Both Cs* and I - have large atomic size.
95. KCl has FCC structure.
1 mole = 6 x 1023 molecules of KCI
4 molecules in 1 unit celI
.'. 6 x 1023 molecules - 1.g x 1023 unit cells
96. It is a ccp structure.
.'. Number of oxide ions (O2 - ) are 4.
.'. Total negative charge - 4 x (- 2) - - 8
Let number of AI 3*
be r and number of Mg'*
be .y.
@
84
d=
5.0 =
o3=
a=
l/A . a3
2x6.9
6x 1023 xo3
2x6.9
Total positive
3r+ 2Y=8
charge-3x+2y
(to balance the negative
charge due to oxide ions)
is the only value satisfying
2.3 x
cm.
10- 23
.*3
x-2andY=l
the equation.
n - fraction of octahedral holes occupied by
r), 2 1
lrr
4 2'
6 x 1023
2.84 x 10- 8
I

27. MHT.GET + CHEMISTRY
m - fraction of tetrahedral voids occupied by
Ms'* = +.
8
97 . F or each Sr2* ion introduced two Na* ions
are removed; creating a cation vacancy.
10-
a
mol percent of SrCl2 is added.
'.'. 100 mol NaCI are doped with 10- 4
mol
100
moI NaCl,
= 10- 6
mol SrC12 is added.
No. of Sr2* ions added
= 10-6 x 6 x 1023 = 6 x 1017
No. of cation vacancies = 6 x 1017.
106. Since pairs of ions are missing at lattice
points mass of the crystal decreases but vol-
ume remains same. Hence, density decreases.
L07 . On heating ZnO loses oxygen and turns
yellow.
The excess Zn2* ions are trapped in the
interstitial sites and electrons also occupy
interstitial po sitions .
zno
o
, zn2* **o, +2e_
2
108. The holes created by missing anions are
occupied by electrons. These sites are called
F-centres and are responsible for colour in
the crystal.
110. The oxide is Ms.gsO.
For one mole of the oxide; moles of 02 - - 1.
moles of M - 0.98.
Let, moles of M 3*
= *
.'. Moles of M 2+
- (0.98 - x)
On balancing charges;
[3r] + t(0.e8 - x) 2) + l- 2l -- 0
000
M3* M2* 02-
x - 0.04
% ofM 3*
Solid State
1 11. Metal deficiency defect occurs with metals
showing variable valency.
FeS, FeO, NiO.
It4. Since it is a metal oxide O
2- is present. A
has oxidation state 2+.
3: J, ilT #"1," ;:t";1, i J :lil;^'.
115. In brass alloy, copper is the host element and
zrrtc is the impurity.
116. A crystal showing interstitial defect either
has the same or higher density.
Schottky defect is shown by elements having
high ionic character.
119. Germanium (group 14) is doped with a
trivalent impurity gallium (group 13). Hence,
a p-type semiconductor is obtained.
120. Metalloids behave as conductors at higher
temperature.
Greater the band gap lesser is the probability
of electrical conductivity. Electrolytes carry
current with the help of free ions.
1-zL Since boron (group 13) is trivalent.
127. CrO2; Fe + ferromagnetic
Cu2* -+ paramagnetic
128. Benzere, N2 and NaCl are diamagnetic.
L29. Ferromagnetic substances can be magnetised
permanently.
131 . 2rS. : [Ar] 3d1 4s2
sc3* [Ar] Bdo4so
Since, S.'* and CzHsOH have no unpaired
electrons, they are diamagnetic.
132. Greater the number of unpaired electrons
greater is the magnetic moment.
L34. Since all electrons are paired, they are dia-
magnetic and the number of electrons with
clockwise and anticlockwise spin should be
same.
135. Maximum magnetic moment.
SrC12.
For 1
10-4
x 100 - 4.08 %

28. MHT-CET + CHEMISTRY Solid State
MISCELLANEOUS EXPLORER
1. A compound of formula AzBs has the hcp
Iattice. Which atom forms the hcp lattice and
what fraction of tetrahedral voids is occupied
by the other atoms?
(a) hcplattice-A,
(b) hcp lattice-A,
(c) hcp lattice-B,
2
(d) hcp lattice-B,
E
Tetrahedral voids-A
Element 'B' forms ccp structure and 'A'
occupies half of the octahedral voids, while
oxygen atoms occupy all the tetrahedral
voids. The structure of bimetallic oxide is
7 . A substance has a face-centred cubic crystal
with a density of 1.984 g cm-3 and edge Iength
630 pm. Calculate the molar mass of the
substance.
(a) 98.63 g mol-1
(c) 74.70 g mol-1
8. The number of atoms in 100 g of an fcc crystal
with density, d,= 10 g/cm3 and cell edge equal
to 100 pffi, is equal to
(a) 2x 1025 (b) 1x lo25
(c) 4x1025 (d)BxLo25
9. Percentages of free space in cubic close
packed structure and in body centered packed
structure are respectively
(a) 30 % and 26 % (b) 26 % and 32 %
(c) 32 % and 48 % (d) 48 %o and 26 %
10. Lithium forms body centred cubic structure.
The length of the side of its unit cel1 is 351
pm. Atomic radius of the lithium will be .
Tetrahedral voids-B
Tetrahedral voids-B
Tetrahedral voids-A
(b) AaBzO
(d) AzBO+
(b) o.e3 A
(d) 3.22 A
(b) 0.134 a
(d) 0.067 a
(a) 75 pm
(c) 240 pm
(b) 85.50 g mol-1
(d) 63 .45 g mol-l
(b) 300 pm
(d) t52 pm
i;; ;" zo+
(c) A2B2O
o
(a) 5.72 A
(c) 1.86 A
(a) 0.027 a
(c) 0.047 a
2
;
D
1
3
1
3
2.
3. A metal crystallises into a lattice containing
a sequence of layers as ABABAB.... What
percentage of voids are left in the lattice?
(a) 72 % (b) 48 % (c) 26 % (d) 32 %
A metal crystallises in a face centred cubic
structure. If the edge length of its unit ceIl is
a, the closest approach between two atoms
in metallic crystal will be .
(d) z J-z a
Sodium metal crystallises in a body-centred
cubic lattice with a unit ceII edge of 4.29 i.
The radius of sodium atom is approximately
11. The radius ratio in CsCI is 0.93. The expected
lattice structure is ..
(a) tetrahedral (b) square planar
(c) octahedral (d) body-centred cubic
12. In the fluorite structure, the co-ordination
number of Ca3
*
io., is ..
(a) 4 (b) 6 (c) 8 (d) 3
13. The appearance of colour in solid alkali metal
halides is generally due to .
(a) Schottky defect (b) Frenkel defect
(c) Interstitial positions
(d) F-centre
L4. What is the number of tetrahedral voids per
atom in a crystal?
(a) 1 (b) 2 (c) 6 (d) 8
15. To get a n-type semiconductor, the impurity
to be added to silicon should have which of
the following number of valence electrons
(a) 1 (b) 2 (c) 3 (d) 5
4.
(a) Ji o (b)
-J,
(c) 2a
-
b.
6. The radius of the largest sphere which fits
properly at the centre of the edge of a body
centred cubic unit cell is .. . (edge length is
represented by o)
f
/.

29. MHT-CET + CHEMISTRY Solid State
ANSWERS
1. (c)
6. (d)
1 1. (d)
2. (a)
7. (c)
12. (c)
3
8
13
(c)
(c)
(d)
4 (b)
(b)
(b)
I
t4
b
10
15
(c)
(d)
(d)
HINTS AND SOLUTIONS
Let number of atoms of B used in packing
- n Number of tetrahedral voids - 2n.
If A occupies 1/3 tetrahedral voids, then
F or bcc,
b.
1.
r= 6
4
6 x
4
4.29 = 1.86 A
2.
A= +
x2n-?"
A:B=
2 2
;n:n=;:t=2:3
6.
Thus, formula AzBs.
Number of atoms per unit cell Ln ccp - l/ - 4
Number of octahedral voids - l/ - 4
A occupies half of the octahedral voids, thus,
A atoms per unit cell = 412 - 2.
Tetrahedral voids - 2 x l/- 8.
So number of oxygen atoms - 8
A:B:O::2:4:8
Thus, structure of bimetallic oxide is AB2O4.
ABAB packing is hexagonal close-packing in
which all atoms occupy 7 4 % of the total
space. Hence, 26 % of voids are left in the
lattice.
For fcc, 7.
ZxM
IV A, o3
1.984 x 6 .023x 1023 x (630 x 10-10)3
a = 2 (R + r)
a
... ,=(R+r)
F or bcc, .li
" = 4R
Using (i) and (ii),
a "Ji
=
24
..... (i)
..... (ii)
3.
24
(z-.6)
-al l=0.067a
1,4)
4. p=
tu[-
B
G
Therefore, distance of closest approach
4
= 74.70 s mol-1 [ For fcc, Z = 4)
Mass (m) = 100 g; Density (d) = 10 g/cm3 and
rength (/) =
i;; :Tr: l,x1o_12 ^
vorum"lffi:l;",l
Jr
_ 1O-24.*3
Volume of 100 g of element
=
Mass _ 100 ^-^ 3
Density 10 = 1o cm"
I
I 8.
ED
thenb-4r=J-Zo
4t
Cl=-
l; - 2J-z
'
-2r=2x L
2J'
a
r_-
' 2J-2
a
Jz

30. MHT.CET + CHEMISTRY
Therefore, number of unit cells
10
=
@ =1025
Since each fcc cube contains 4 atoms.
Therefore, total number of atoms in 100 g
4 x 1025
9. Packing fraction is defined as the ratio of the
volume of the unit cell that is occupied by
the spheres to the volume of the unit cell.
P.F. for ccp and bcc are 0.74 and 0.68
respectively.
So, the free space in ccp and bcc are 26 %
and 32 % respectively.
10. For bcc structure, ..6 a - 4r
r= Er=6 x351 = tb1pm.
4,4
Solid State
Since the radius ratio of CsCl is 0.93, it is
expected to have a body centred cubic
structure.
12. In fluorite structure each F - ion is
surrounded by four Caz
*
ions where as each
Caz
* is surrounded by eight F - ions, giving
a body centred cubic arrangement. Thus the
co-ordination number of Caz
* and F - are 8
and 4 respectively.
13. The appearance of colour in solid alkali metal
halide is due to presence of F -centre found
as defect in the crystal structure.
14. Number of tetrahedral voids ffr) in a crystal
is twice the number of atoms (n) in a crystal,
i.e., Yr = 2n
So, number of tetrahedral voids per atom is
givenbyVrln=2.
15. For n-type, impurity added to silicon should
have more than 4 valence electrons.
@
11
PREVl0UsYEAR0UEsTl0NSffiffiiiil:.::::::i:::..:.i..:::::...
=
D.
1.
MHT-CET 2014
Which among the following solids crystallises
as a face centered cube?
(b) Rubidium
(d) Platinum
In which among the following solids Schottky
defect is not observed?
(a) ZnS (b) NaCl (c) KCI (d) CsCl
If a metal crystallises in BCC structure with
edge length of unit cell as 4.2g x 10- 8
cm;
the radius of the metal atom is
(a) 3.2 x 10- t .* (b) 1.07 x
(c) 1.07 x 10-
t .rr, (d) 1.86 x 10-
t .*
Which among the following statements is
true about Schottky defect?
(a) In this type of defect, regular cation is
replaced by a different cation.
(b) tr'ormation of a metal alloy is an example
of this defect.
(c) In this type of defect; cation or anion
moves from regular site to a place between
Iattice sites.
(d) In this defect, cation and anion are in
stoichiometric proportion.
(a)
(c)
Iron
Uranium
In a face centred cubic cell, what the volume
occupied?
@) !nr3 (b) 9 nf (.1 E nr3 (d) 64-r'
/ 3 / 3 3 /
3J3
3. Which among the following solids is a non - 7.
polar solid?
(a) Hydrogen chloride (b) Water
(c) Sulphur dioxide (d) Carbon dioxide
4. What is the hybridization of carbon atoms in
fullerene?
(a) sp3 ft) sp
6.
2.
;;- i .*
I
I
(c) sp2 (d) dsp3

31. - M
@
not
8.
HT-CET + CHEMISTRY
Which among the following statements is
true about amorphous solids?
(a) They are pseudo solids.
(b) Values of physical properties change with
direction of measurement.
(c) They behave like fluids.
(d) They are supercooled liquids.
9. Which among the following solids shows
Frenkel defect?
(a) NaCI (b) CsCl (c) AgCI (d) KCI
10. Which among the following pairs of com-
pounds is not isomorphous?
(a) K2SO4 and K2SeOa
(b) NaNO3 and CaCO3
(c) NaF and MgO
(d) NaCI and KCI
11. How many total constituent particles are
present in simple cubic unit cell?
(a) 1 (b) 3 (c) 4 (d) 2
t2. The percentage of unoccupied volume in
simple cubic cell is ........
(a) 52.42 % (b) 32 %
(c) 47 .60 % (d) 6 8.01%
,,.,.,::.,i,,
13. The edge length of FCC type unit ceIl
copper having atomic radius 127.6 pm
equal to .
(a) 295 pm
(c) 361 pm
L4. What is the number of atoms present per unit
cell of aluminum having edge length 4 A?
17. An element crystallises in a BCC lattice with
cell edge of 500 pm. The density of the
element is 7 .5 g cm 3.
Ho* many atoms are
present in 300 g of metal?
(a) 1.6 x 1023 atoms (b) 3.2 x 1023 atoms
(c) 6.4 x 1023 atoms (d) 12.8 x 1023 atoms
18. Silver crystallises in FCC structure. If the
edge length of the unit cell is 316.5 pffi, what
is the radius of the silver atom?
(a) 158.25 pm
(c) 137.04 pm
(b) 1 11.91 pm
(d) 12t 91 pm
19. An element has a BCC structure with cell
edge of 288 pm. The density of the element is
7 .2 g cm-3. What is the atomic mass of the
element?
(a) 62.43 (b) 51.78 (c) 77.68 (d) 25.8e
20. How much part of an atom occupies each
corner of a BCC unit cell?
1111
(a)
2
(b)
6
(c)
8
(d)
4
21. Sodium crystallizes in BCC structure with
radius 1.86 x 10- 8 cm. What is the edge
length of a unit cell of sodium?
(a) 5.26 x 10-8 cm (b) 4.3 x 10-8 cm
(c) 7 .44 x 10-8 cm (d) 3.72 x 10-8 cm
22. What is the mass of an FCC unit cell if mass
of one atom of the unit cell is 6 x 10- " g?
(a) 2.4x10-"s (b) 24x 10-"g
(c) 4x10-"s (d)2.4x10-"s
23. What is the percentage of void space in BCC
type of unit cell?
(a) 26 % (b) 32 % (c) 68% (d) 74%
24. What is the coordination number of the cation
in ionic compound if the type of hole occupied
by the cation is octahedral?
(a) 6 (b) 3 (c) 4 (d) 8
25. Which among the followittg is an example of
amorphous solid?
(a) Glass
(c) Diamond
26. How many number of unit cells are present
in 100 g of an element with FCC crystal
having density 10 g/cm3 and edge length
100 pm?
(a) r.25 x 1021
(c) 2.0 x lo24
Solid State
(b) 2.0 x 1023
(d) 2.0 x 1021
(b) Magnesium
(d) Camphor
of
is
15. Lithium crystallises into a body centred cubic
structure. What is the radius of lithium if the
edge length of its unit cell is 351 pm?
(Density of A1 = 2.7
AI = 27)
(a)8 @)4
(a) 151.98 pm
(c) 300.50 pm
(b) 378 pm
(d) 331 pm
g cm 3;
Atomic mass of
(c) 2 (d) 1
(b) 240.80 pm
(d) 75.50 pm
16. An element crystallises in FCC type unit cell.
The volume of one unit cell ts 24.gg x I0- 24
.*3 and density of the element is 7 .2 g cm-3.
Calculate the number of unit cells in 36 g of
pure sample of the element.

32. MHT-CET + CHEMISTRY
(a) 2x7025 0)Bx1025
(c) 4x1025 (d)1xtO25
27 . What is the packing efficiency of F CC crystal
structure?
(a) 52.4 % (b) 7 4.0 %
(c). 68.04 % (d) 47 .6 %
MHT.GET 2021
28. Identify the type of unit cell that has particles
at its eight corners and an additional particle
at the centre of the cube
(a) F ace centered cubic unit cell
(b) Simple cubic unit ceII
(c) Body centered cubic unit cell
(d) Hexagonal close packed unit cell
29. How many octahedral voids are present in
1 mole of a compound that forms HCP
structure?
(a) 3.011 x 1023
(c) 2.4 x 1023
(b) 6.02 x 1023
(d) t.2 x 1023
30. What is the molar mass of a crystal having
BCC unit cell with edge length 5 A and
density 2 glmL?
(a) 90 S moI-l
(c) 45 S mol-1
31. Which among the following is ferromagnetic?
(a) Zn (b) Sc (c) Cu (d) Ni
32. What is the percentage of unoccupied volume
in BCC structure?
(a)32% (b)74% (c)26% (d)68%
33. What is the total number of atoms in BCC
crystal lattice having 1.8 x 1020 unit cells?
(a) 7.2 x 1o2o 1b) 9.0 x 1o2o
(c) 1.8 x 1o2o (d) 8.6 x 1o2o
34. What is the density of an element (atomic
mass 100 g mo1-1) having BCC structure with
edge length 400 pm?
Solid State
(c) Their densities are Iess than parent
metal.
(d) The;metting points are higher than pure
36. What is the percentage efficiency of packing
in BCC structure?
(a)68% (b)74% (c)32% (d)26%
37. An element with simple cubic close structure
has edge length of unit cell of 3.86 A. Wfrat is
the radius of the atom?
(a) 3.86 x 10-8 .-
(c) 5.79 x 10-
8
.*
(b) 1.93 x 10-8 .*
(d) 2.43 x 10- B
.*
38. What is the volume of the unit cell of a metal
(atomic mass 25 g mol-1) having BCC
structure and density 3 g .*- 3?
(a) 2.7 6 x 10- '3 .rr,' (b) 8.64 x 10- '3 .*3
(c) 1.56 x 10- 2n
"^3
(d) 1.88 x 10- 2n
,^3
39. What is the coordination number of atoms in
BCC crystal lattice?
(a) 6 (b) 8 (c) 2
35. Which property from the following is NOT
exhibited by interstitial compounds?
(a) These are hard and good conductors of
heat and electricity.
(b) Their chemical properties are different
than parent metal.
(d) 4
40. What is the density of potassium if it has BCC
structure with edge length 4 A? (Atomic mass
ofK=39)
(a)3g.--3 (b) 2g.*-3
(c) 5gc--3 (d)4gcm-3
4L. How many tetrahedral voids are present in
1 mole of a compound that forms hcp
structure?
(a) 0.1 mole (b) 2.0 mole
(c) 0.5 mole (d) 1.0 mole
42. How many atoms of niobium are present in
2.43 g if it forms BCC structure with density
9 g cm 3
and volume of unit cell 2.7 x 10- 23
3.t
cm!
(a) 4.t x lO22
(c) 2.0 x tO22
43. How many tetrahedral voids are present in
0.4 mol of a compound that forms hcp
structure?
(a) 4.8 x 1023 ft) 1.2 x 1023
(c) 2.4 x 1023 (d) 3.011 x 1023
44. Identify the type of unit cell that has particles
at the centre of each face in addition to the
particles at the eight corners of a cube.
(a) Face centered cubic unit ceIl
(b) 60 g mol-1
(d) 75 g mol-1
(b) 5.18 g .*- 3
(d) 4.8 g .-- 3
(b) 5.0 x to22
(d) 3.01 x 1023
(a) 8.2 g cm- 3
(c) 3.2 g cm- 3

33. MHT.CET + CHEMISTRY
(b) Body centered cubic unit cell
(c) Simple cubic unit ceII
(d) Hexagonal unit cell
45. Which of the following is the correct repre-
sentation of the relation between radius of
sphere and the edge length in simple cubic
crystal?
(a) r
(c) r
46. A compound having BCC structure has
atomic mass 50. What is the density of the
unit cell if edge length is 300 pm?
(a) 4.7 g cm- 3 ft) 5.1 g .-- 3
(c) 6.1 g .*- 3 (d) 7.4 g cm- 3
47. If edge length of BCC crystal is
10
-
x 10 -10 * , then the atomic radius is
Js
Solid State
A metal has BCC structure with edge length
of unit ceII 400 pm. Density of metal is
4 g .-- 3.
What is the molar mass of the
metal?
(a) 92 S mol-l
(c) 27 S mol-l
(b) 40 S mol-1
(d) 77 S mol-1
52. The F CC unit cell of a compound contains
ions A at the corner and ions of B at the centre
of each face. What is the formula of the
compound?
(a) AzB (b) AB3 (c) AB (d) AB2
53. What is the atomic radius of polonium if it
crystallises in a simple cubic structure with
edge length of unit cell 336 pm?
(a) 84 pm (b) 234 pm
(c) 168 pm (d) 336 pm
54. Identify ferromagnetic element from the
followirrg.
(a) Manganese (b) Vanadium
(c) Chromium (d) Iron
55. An element with BCC structure has edge
length of 500 pm. If its density is 4 g cffi- 3,
find atomic mass of the element.
(a) 150 g mol-l
(c) 100 g mol-l
(b) 250 g mol-1
(d) t25 g mol-l
56. How many particles per unit cell are present
in BCC structure?
(a) 1 (b) 2 (c) 3 (d) 1
57. What is the total number of Bravais lattices
present in seven types of crystal system?
(a) 7 (b) 10 (c) 72 (d) L4
58. What is the molar mass of metal with BCC
structure having density 10 g cm 3
and edge
length 200 pm?
(a) 90.2 g mol-1
(c) 24.1 g mol-1
59. How many total voids are present in 1 mole
of compound that forms hcp structure?
@
51
a
=-
J'
a
2
(b) 0 =;
(d) a-
E
(b) ".,6"10-10m
(d) 2.5 x 10-10 m
48. An element has BCC structure with edge
length of unit cell 600 pm. What is the atomic
radius of the element?
(a) 150 pm (b) 300 pm
(d) 16"150pm
49. The density of chromium metal is 7 g cm- 3.
If the edge length of the unit cell is 300 pffi,
identify the type of unit ceII.
(Atomic mass of Cr = 52)
(a) Face centered cubic
(b) Body centered cubic
(c) Simple cubic
(d) Hexagonal close pack
50. What is the volume occupied by particles in
BCC structure tf a is the edge length of the
(a)
+x 1o-1o rn
(c) 2.25 x 10-10 m
300
(c) pm
'12
(a)
(c)
6.022 x 1023
3.011 x 1023
(b) 60.5 g mol-1
(d) 48.0 g mol-1
(b) 1.806 x 1024
(d) 1.204 x tO24
unit cell?
Jgno'
(a)
8
no3
(c)
72 ",12
3
TEA-
(b)
342
(d) G no'
16

34. MHT-CET + CHEMISTRY Solid State
ANSWERS
1. (d)
6. (d)
1 1. (a)
16. (b)
21. (b)
26. (d)
2. (c)
7. (d)
12. (b)
17. (c)
22. (d)
27. (b)
3. (d)
g. (b)
13. (c)
18. (b)
23. (b)
28. (c)
4. (c)
9. (c)
14. (b)
19. (b)
24. (a)
29. (b)
5. (a)
10. (a)
15. (a)
20. (c)
25. (a)
30. (d)
31. (d)
36. (a)
41. (b)
46. (c)
51. (d)
56. (b)
32. (a)
37. (b)
42. (c)
47. (d)
52. (b)
57. (d)
33. (d)
38. (a)
43. (a)
48. (d)
53. (c)
58. (c)
34. (b)
39. (b)
44. (a)
49. (b)
54. (d)
59. (b)
35. (b)
40. (b)
45. (c)
50. (a)
--/
bb. (a)
HINTS AND SOLUTIONS
2. FCC has 4 atoms per unit cell.
. 4 3 16 3
.'. Volume occupied - 4
" g
Ttr' - Tn,
Pyrex glass contains 60 to 80% SiOz, 10 to
25 % BzO3 and remaining amount is A12O3.
For BCC,
=
J-g
" * 1.722 x 4.2g x LO-'
4 atoms are present in one FCC unit cell.
8 x 1023 atoms are present in 2 x 1023
FCC unit celIs.
1g. ,=+= "u',t-,-111.91 pm
zJ, 2xt.4l4 rr^
22. Mass of 1 atom = 6 x 10- " g
Mass of 4 atoms (FCC unit cell)
= 4x 6 x 10-23 - 24x 10-" g
= 2.4x 10-" g.
29. Number of octahedral voids is equal to
number of atoms present.
(1 mole = 6.023 x 1023 atoms/molecules)
2M
3.
6.
4
.'. r =1.857x
8. Amorphous solids
4
10-
8
.-
are isotropic.
13. r=+
2,12
... a = 127.6x2x1.414
= 360.8 pm
L4. a=4A'=4x 10-8.-
ZM
30. d=
M-
d=
=
d=
r=
r=
LIA.o3
2x6x1023 x (5 x 10-t)'
d=
Z_
NA 'o'
dNl'o3
M
2.7 x 6.022x1023 x @x 10-t)3
27
= 151.98 pm
.'. fu[ - 75.27 g mol-l.
33. Number of atoms per unit cell of BC C = 2
.'. Total number of atoms in 1.8 x 1020 unit
cells - 2 x 1.8 x 1o2o - 3.6 x 1020.
34. For BCC,
2M
2
=3.85=8
Ji" -t.732x35t
15. r=
16.
o
4
d
4
4M
l/A . a3
7.2x6.022x 1023 x24.99x 10-
l/A . o3
2x100
6x1023 x@x10-8)3
5.189 g cm- 3.
a 3.86 x 10-8
-=
22
1.93 x 10-8..rr.
M-
M-26.989mol-1
26.98 g contains 6.022 x 1023 atoms.
.'. 36 g contains 8 x 1023 atoms.
37. For SCC,

35. MHT-CET + CHEMISTRY
2M
38.
- 2.77 x 10-'3 .*3
Solid State
ZM
I{A.o3
7 x 6.022x 1023 x (3 x 10-t)*
2.18 = I
ZM
52
... BCC.
l/A . oZ
2xM
(6.022x 10")@ x 10-t)'
= 77.08 g mol-l.
X 8-1
X6=
40.
d=
o3=
l/A . o3
2x25
49. d=
51. d=
6 x 1023 x 3
2M
Z=
Z=
IVA-o3
2x39
6.022x1023 x(4 x 10-t)'
d = 2.02 g cm-
3.
4L. Ratio of atoms to tetrahedral voids is
2M
42. a =
l/A . ao
2 x Mass of substance
Number of atoms x q,3
2 x 2.43
Number of atoms x (2.7 x 10 - 23
)3
Number of atoms - 2.0 x 1022.
43. 0.4 mol of compound will contain 0.8 mol of
tetrahedral voids.
.'. N,rmber of tetrahedral voids
=0.8x6.022x1023
= 4.8176 x 1023 voids.
2M
46.
l/A . o3
2x50
=
d=
47. For BCC,
r=
=
48. r =
52. Ions A at the corner
Ions B at the face centre .'.
tr'ormula is ABg.
a 336
1:2.
4
M
1
8
1
2
=
.o
53. r-
bb.
59.
22
d=
IVA.o3
4 x 6.022x 1023 x (5 x 10-t)u
.'. fu[ -
.'. fu[ - 150.5 g mol-l.
56. Number of atoms per unit cell in BCC = 2.
2M
- 168 pm.
2M
l/A . o3
10 x 6.022x 1023 x (2x 10-t)'
d=
ll/[ -
(6.022x 10")
"
(3 x 1o-8)3
6.150 g .*- 3.
r-J-so
4
.610
X: x 10-10
4Js
2.5 x 10-
1o
-
G^
4 " for BCC
18x6x10-8
4
.f;x1.5x10-8.*
.f; x 1.5 x 10-10 m
.E x 150 x 10-12 m.
.'. fu[ - 24.08 g mol-l.
59. 1 mole of compound contains 6.022 x 1023
atoms
Number of octahedral voids - 6 .022 x 1023
Number of tetrahedral voids
= 2xG.0Z2x 1023
= 12.044 x 1023
Total number of voids
= 1g.066 x 1023
= 1.g066 x L024.

36. MHT.CET + CHEMISTRY Solid State
TEST YOUR KNOWLEDGE
1. If a non-metal is added to the interstitial sites
of a metal, then the metal becomes .
(a) softer (b) Iess tensile
(c) Iess malleab1e (d) more ductile
An element occurring in the BCC structure
has L2 x 1023 unit cells. The number of atoms
of the element in these cells is ..
(a) 24 x 1023 1b) 86 x 1023
(c) 6 x 1023 (d) t2 x 1023
Crystalline solids are ........
(a) true solids. (b) molecular solids.
(c) pseudo solids.
(d) supercooled liquids.
A metal of atomic mass 60 g mol -1 hur a BCC
crystal structure. If the density of the metal
is 3.6 g cffi- 3, the volume of the unit cell
is ..
(a) b.b5 x 10- 23
.*3 (b) 0.b5 x 10-'3 .*3
(c) 55.5 x 10-
23
.*3 (d) b.55 x 10-'5 .*3
Paramagnetic substances shows a magnetic
moment due to .
(a) one or more unpaired electrons.
(b) paired electrons.
(c) spin of electrons.
(d) equal number of parallel and antiparallel
spins of electrons.
A given metal crystallises in a cubic structure
having edge length 360 pm. If there are two
metal atoms in one unit cell what is the
radius of one atom?
(a) 108 pm
(c) 156 pm
(b) 40 pm
(d) 80 pm
Which metal among the following has highest
packing efficiency?
(a) Tungsten &) Platinum
(c) Aluminium (d) Both (b) and (c)
For an ionic solid; the particles which occupy
the lattice points are ........
(a) molecules (b) ions
(c) protons (d) atoms
Copper crystallises in a FCC lattice with a
unit cell length of 361 pm. The radius of the
copper atom in pm is ..
(a) t57 (b) 181 (c) 108 (d) L28
10. To get n-type semiconductor the impurity to
be added to silicon should be .
(a) pentavalent.
(b) having 5 valence electrons.
(c) from group 15 of the periodic table.
(d) all the above.
11. The fraction of the total volume occupied by
the atoms present in a simple cube is
@)4 &)4
3 J' -/
4J'
12. If a*bic and a*
system is ........
(a) monoclinic
(c) tetragonal
2.
3.
@)I (d) +
b
4.
$*y+90"; thecrystal
(b) triclinic
(d) orthorhombic
13. Frenkel defect is not observed in case of ..
(a) NaCI (b) AgCl (c) CaF2 (d) ZnS
14. The number of octahedral voids present per
atom present in a cubic close packed struc-
ture is ..
(a) 1 (b) 3 (c) 2 (d) 4
15. The crystal system of a compound with unit
cell dimensions a = 0.387, b = 0.387 and
c = 0.504 nm and cr - B = 90" and y = l20o
is ..
(a) cubic (b) hexagonal
(c) orthorhombic (d) rhombohedral
16. Stoichiometric defects are also known are
(a) substitutional impurity defect
(b) intrinsic defect
(c) thermodynamic defect
(d) both (b) and (c)
L7 . What is the energy gap between valence bond
and conduction band in insulators?
(a) Both bands overlap
(b) Very small
(c) Infinite (d) Very large
18. Oxygen and Cr3
*
are
(a) diamagnetic (b) paramagnetic
(c) ferromagnetic (d) ferrimagnetic
-
b.
6.
sl
l.
8.
9.

37. MHT-CEr + CHEMISTRY @
L9. A particular solid is hard and brittle. It does 20. The coordination number is ........
not cond"uct electricity in the solid state but
is electrolyte in the aqueous state; hence it
is ........
(a) a molecular solid (b) ionic solid
(c) a network solid (d) covalent solid
Solid State
(a) the number of particles that a given
particle in the unit celI is in direct contact
with.
(b) the ratio of anion to cation.
(c) the ratio of cation to anion.
(d) the ratio of particles to voids.
ANSWERS
1. &)
(c)
6.
2. (a)
(d)
7.
3. (a)
(b)
8.
4. (a)
g. (d)
b.
10.
(a)
(d)
trtrtr
11. (d)
16. (d)
12. (b)
17. (d)
13.
18.
(a)
(b)
L4.
19.
(a)
(b)
15.
20.
(b)
(a)