QUESTION BANK OF SOLID STATE
LEVEL 1
1.
How does
amorphous silica differ from quartz?
2.
Why glass
is called supper cooled liquids?
3.
Some of
the very old glass objects appear slightly milky instead of being transparent
why?
4.
What is
anisotropy?
5.
What is
the coordination number of atoms?a) in fcc structure b) in bcc structure.
6.
How many
lattice points are there in one cell of a) fcc b) bcc c) simple cubic
7.
What are
the co‐ordination numbers of octahedral voids and tetrahedral
voids?.
8.
Why common
salt is sometimes yellow instead of being of being pure white?
9.
A compound
is formed by two elements X and Y. The element Y forms ccp and atoms of X
occupyoctahedral voids. What is formula of the compound?
LEVEL 2
1.
Explain
how electrical neutrality is maintained in compounds showing Frenkel and
Schottkydefect.
2.
Calculate
the number of atoms in a cubic unit cell having one atom on each corner and
twoatoms on each body diagonal.
3.
Gold
crystallizes in an FCC unit cell. What is the length of a side of the cell(r=0.144mm)?
4. Classify each of the following as
either a p‐type or n‐type semi‐conductor.
a) Ge doped with In (b) B doped with
Si
5.
In terms
of band theory what is the difference between a conductor, an insulator and a
semiconductor?
6.
The
electrical conductivity of a metal decreases with rise in temperature while
that of a semiconductorincreases. Explain.
7.
What type
of substances would make better permanent magnets, ferromagnetic
orferromagnetic, why?
8.
Zinc oxide
is white but it turns yellow on heating. Explain?
9.
In
compound atoms of element Y forms ccp lattice and those of element X occupy
2/3rd oftetrahedral voids. What is the formula of the compound?
10.
AgCl is
doped with 10–2mol% of CdCl2, find the concentration of
cationvacancies.
Level Three Hots
Q-1 CsCl have bcc
arrangement and its unit cell edge length is 400 pm.
Calculate interionic distance.
Q-2 Analysis show
that Ni Oxide has formula Ni 0.98 O 1.8 What fractions
of Ni exist as Ni2+ and Ni3+ ions?
Q-3 on terms of
band theory what is the difference
(i) between
conductor and insulators.
(ii) between
conductor and semi-conductors.
Q-4. KF has NaCl structure calculate the edge
length of its unit cell if its
dencity is 2.48 cm-3.
molar mass of KF = 58.1
g mol-1,
NA = 6.02 x 1023 mol-1.
Q5. In the cubic crystal of CSCl d = 3.97g/cm3.
the eight corners are
occupied by Cl- with Cs-
at centre and vice versa .Calculate the distance
between Cs+ and Cl-
ions. What is the radius ratio of two
ions-. (atmass of Cs =
132.9 and Cl = 35.46.
VALUE-BASED QUESTIONS
Q.1 A goldsmith under training was asked
by his boss to make bangles of gold. He used a bar of 24carat for this purpose
, The bangles made by him were so soft that they could be easily bent. The boss
told him not to use pure gold but rather 22 carat gold. The bangles were now
quite hard and could not be bent on applying some force?
(a)
What was the mistake commited by goldsmith?
(b)
Why did boss ask him to use 22 carat gold?
(c)
In what way is 22 carat gold better than 24 carat gold?
(d)
What is the value associated with this?
Q.2
A student
working in the laboratory passed electric current through a rod of copper as
well as solid copper sulphate crystals . To his surprise, the current could pass
through copper rod connected in a cell and not through the crystals .
(a)
was his observation correct?
(b)
what was the reson behind this observation?
(c)
how is this behaviour helpful in explaning conducting of electrolytes?
Q.3 In India , there is shortage of
electricity . people have to face big cuts particulary when the summer is in
peak . Industry has to suffer a lot . conventional sources of electricity such
as hydel power, thermal power and even nuclear power etc.fail to meet the ever
growing demand of electricity . now a days , there is emphasis on the use of solar energy . photovoltaic material can
convert solar energy into electrical energy.
(a)
what are the drawbacks of traditional source of energy?
(b)
how is solar energy better than conventional source of energy
(c)
why is solar power not very popular in india?
(d)
what is the value associated with the use of solar energy?
Q.4
Daimond
and graphite are two crystalline allotropic forms of carbon . however , they
differ in most of their physical characteristis. for example , diamond is very
hard while graphite is quite soft. Daimond is a poor conductor of e.lectricity
. on the other hand , graphite is a good conductor . Answer the following
questions.
(a)why
is diamond hard while graphite is soft?
(b)why
is diamond a poor conductor of
electricity while graphite is a good conductor?
(c)
why are certain diamonds very shining?
(d)
what is the value associated with the diamonds?
Q.5 Sudanshu made a model of
the unit cell of diamond. It resembled the unit cell of ZnS. If the unit cell
of ZnS has 4 units of ZnS per unit cell. It has the same packing efficiency as
ZnS. But diamond is the hardest known substance.
(a)What is the number of atoms of carbon per unit cell of diamond?
(b)What is the value that Sudanshu can derive from these facts?
(c)What is the value that Sudanshu can derive from these facts?
QUESTION
BANK - SOLID STATE (ANSWERS)
LEVEL 1.
Ans1. In amorphous silica, SiO4
tetrahedral are randomly joined to each other whereas in quartz they
arelinked in a regular manner.
Ans2.Schottky defect.
Ans3. It has tendency to flow like
liquid.
Ans4. Due to crystallization
Ans5. Physical properties show
different values when measured along different directions in crystalline solids
Ans6. a) 12 b) 8
Ans7. a) 14 b) 9 c) 8
Ans8. 6 and 4
respectively
Ans9. Due to the presence of electrons in some lattice sites
in place of anions these sites act as F‐centers.These electrons when excited
impart color to the crystal.
Ans10. No. of Y atoms be N No. of
octahedral voids N
No. of X atoms be =N Formula XY
LEVEL 2.
Ans1. In compound showing Frenkel
defect, ions just get displaced within the lattice. While incompounds showing
Schottky defect, equal number of anions and Cations are removed fromthe
lattice. Thus, electrical neutrality is maintained in both cases.
Ans2. 8 corner *1/8 atom per unit cell = 1atom
There are four body diagonals in a
cubic unit cell and each has two body centre atoms.
So 4*2=8 atoms therefore total
number of atoms per unit cell =1+8=9
Ans3. r=0.144nm
a=2*√2r
=2*1.414*0.144nm
=0.407nm
Ans4. (a) Ge is group 14 elements
and In is group 13 element. Therefore, an electron deficit holeiscreated. Thus
semi‐conductor is p‐type.
(b) Since B is group 13 element and
Si is group 14 elements, there will be a free electron, thus it is n type semi
conductor.
Ans5. The energy gap between the
valence band and conduction band in an insulator is very large while in a
conductor, the energy gap is very small or there is overlapping between valence
band andconductionband.
Ans6. In metals with increase of
temperature, the kernels start vibrating and thus offer resistance to the flow
of electrons. Hence conductivity decreases. In case of semi‐conductors, with increase oftemperature, more electrons can
shift from valence band to conduction band. Hence conductivity increases.
Ans7.. Ferromagnetic substances make
better permanent magnets. This is because the metal ions of a ferromagnetic
substance are grouped into small regions called domains. Each domain acts as
tiny magnet and get oriented in the direction of magnetic field in which it is
placed. This persists even in the absence of magnetic field.
Ans8. When ZnO is heated it looses
electron and which occupies the
interstitial sites . This electron absorbs the radiation from the
visible region and transmitted radiations and reflects the colour.
Ans9.
No. of Y atoms per unit cell in ccp
lattice=4
No. of tetrahedral voids= 2*4=8
No. of tetrahedral voids occupied by
X= 2/3*8=16/3
Therefore formula of the compound =X16/3
Y4
=X16 Y12
=X4 Y3
Ans10. Doped atom = 10–2mol%
of CdCl2
= 10–2 x 6.022 X 1023 atoms.
One crystal of CdCl2
create one cation vacancy when doped with AgCl
No of cation vacancies = 6.022 X 1021
LEVEL 3.
Ans1 Face Diagonal = √a2
+a2 = √ 2 .a
Body Diagonal = √(√2a)2 + a2
Body Diagonal = √3 . a .
Body Diagonal= √3 x 400 = 1.73x400
Body Diagonal = 692
Interior Distance = ½
x Body Diagonal = ½ x 692 = 346pm.
Ans 2. Ni 2+
ions present the ratio of Ni : O is 1:1
i.e, 100Ni2+ ion should
have 100 O2-. Now replace 3Ni2+ ions
2Ni3+ ions are required it
means presence of two Ni3+ would reduce one No. of Ni out of 100
numbers.In Ni 0.98 O 1.00 ratio 98:100. It means two Ni ions are lesser
than oxide ions ( out of 100 atoms) Then four Ni3+
ions are present
and 96 Ni2+ are present for each 100 oxide ions.
Thus % of Ni2+ is
96% and Ni3+ is 4%.
Ans3.
(i) in conductor the
energy bands are very close overlapped by the
conduction bands. Due to this reason e- can flow
very easily from
valency band to conductor band under an electric field,
thereby
showing conductivity.
ii) In semiconductor the gap between valence band and conduction bond is small which make some of the e- enable to jump from valences band to conduction band. Therefore conductance is observed with the increace in temp. more e- jump. Hence the electrical conductivity of semiconductor increase with the increase in temperature.
Ans4. For Nacl
d = 2xM/a3 x NA
a3 = 2 x M /d x NA
a3 = 4 x 581/2.48 x 6.02 x 10-3
= 155.659 x 10-24
a = 5.379 x 10-8 cm
= 537.9 p.m.
Ans5. In one unit cell there is one CsCl 1/8 x 8 Cl- + 1 Cs +
d = z x M/a3 x Noa3 = 2 x M / d x No
a3 = volume , Z = 1m = 132.9 + 35.46 = 168.36
f = 3.97 g cm-3No = 6.02 x 1023.
a3= 1 x 168.36/6.02 x 1023 x 3.97 = 7.04 x 10-23 cm3
a = (7.04 x 10-23)1/3a = 4.13 x 10-8 cm = 413 pm.
Hence the diagonals = √3 x 413 = 715.34 pm.
As the structure with Cs+ at centre and Cl- at corner
2r+ + 2r- = 715.34 or
r+ + r- = 715.34 / 2 = 357.62 pm
We assume 2Cl- touch with each other than length of cell is
2r- = 413 pm
r- = 206.5 pm
r+ =357.67 - 206 .50 =151.17 pm
r+/r- = 151.17/206.50 = 0.73
VALUE-BASED ANSWERS
Ans.1 (a) ornaments are not made from 24 carat gold which is completely pure.
(b) 22 carat gold contains traces of copper or silver as impurity.
(c) It is better than puregold since it is comparatively hard, malleable and ductile.
Infact, 22 carat is an alloy.
(d) The boss guided the junior worker about the technique for making gold jewellery.As stated above , pure gold is extremely soft and is also brittle . That is why bangles could not be made out of that. the information is extremley valuable for all new comers in the field.
Ans.2 (a) yes , his observation was correct.
(b) Copper metal is conducting by the movement of electrons while copper sulphate crystals are expected to be conducting by the movement of ions. Since ions do not move in the solid state therfore , copper sulphate is non-conducting in the solid state.
(c) Electrolytes are either taken in molten state or aqueous solution in the electrolyte cells(e.g. electrolysis,electroplating).They conduct due to the movement of ions.
Ans.3 (a) Traditional source of electricity ;both thermal and nuclear energy lead to emissionof smoke,fly ash and extremely harmful radiations.
(b) Sun is the only source of solar energy of energy in a country like India where the span of summer is very long solar energy is very good option .
(c) Solar power is not very popular in India mainly due to lack of awareness.
(d) Use of solar energy in houese,hotelsand in small industrial unitscan solve our electricity problems.
Ans.4 (a) Structure of diamond is very compact on the other hand graphite has a layer structure.
(b) In diamond all the four valence electrons of carbon are involved in bond formation in graphite three valence electrons of carbon are involved while one electron is delocalised to conduct electricity.
(c) Diamond has a high refractive index as a result certain diamonds produce very high total internal refraction responsible for bluish tinge that is why these are very shiny and expensive.
Ans.5 a) The number of atoms of Carbon per unit cell is 8 in diamond.
b) The C—C bond is very strong in diamond (due to small size of Carbon) unlike the Zn—S bond in ZnS.
c) Though from the same background ie with the same structure the property can be different, thus, with a little effort, we can do same things differently and bring about major change
s.