HOME ASSIGNMENT: UNIT I : SOLID STATE
Prepared By: A P SINGH, PGT-CHEMISTRY,KV KHATKHATI
1.1. How may the conductivity of an intrinsic semiconductor be increased ?
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1.2. Which stoichiometric defect increases the density of a solid ?
(CBSE 2012, 11)
1.3. What are n-type semiconductors ?
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1.4. What type of semiconductor is obtained when Si is doped with As ?
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1.5. Which point defect decreases the density of a solid ?
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1.6. What is the No. of atoms in a unit cell of fcc crystal ?
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1.7. Define forbidden zone of an insulator ?
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1.8. What is the No. of atoms in a unit cell of simple cubic crystal ?
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1.9. State a feature to distinguish a metallic solid from an ionic solid .
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1.10. “Crystalline solids are anisotropic in nature .” What does this statement mean ?
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1.11. Which point in crystal does not change the density of a solid ?
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1,12. What type of interaction hold the molecule together in a polar molecule ?
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1.13. Wrire a distinguishing feature of metallic solid .
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1.14. What is meant by intrinsic semiconductor ?
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1.15. What is the No. of atoms in a unit cell of bcc crystal ?
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1.16. Why LiCl acquire pink colour when heated in Li vapour ?
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2.1. Silver crystallises in fcc structure . Each side of the unit cell has a length of 409 pm .What is the
radius of Ag atom?
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2.2. Calculate the packing efficiency of a metal crystal for simple cubic lattice.
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2.3. Explain how you can determine the atomic mass of an unknown solid if u know the mass density and
the dimensions of unit of its crystal.
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2.4. Define the following terms w.r.t. crystalline solid – (a) Unit cell
(b) Coordination No.
Give example in each case.
2.5. KF has ccp structure. Calculate the radius of unit cell if the side of the cube is 400 pm. How many F –
ions & Octrahedral voids are there in this unit cell.
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2.6. Give reason –
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(a) Why is Frankel defect found in AgCl ?
(b) What is difference between phosphorus doped & gallium doped semiconductors. ?
2.7. Gold (Atomic mass = 197 u, Atomic radius = 0.144 nm) crystallises in a fcc unit cell.
Determine the density of Gold.
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2.8. Classify each of the following as being either a p- type or a n-type semiconductor. Give reason.
(a) Si doped with In
(b) Si doped with P.
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3.1. Copper crystallises with fcc unit cell . if the radius of Copper atom is 127.8 pm , calculate the density
of copper metal . (Atomic Mass of Cu = 63.55 & Avagadro No. = 6.02x 1023 mol-1) (2012, 10)
3.2. Iron has a bcc unit cell with the cell dimension of 286.65 pm . Density of iron is 7.87 g/cc . use this
information to calculate & Avagadro’s No. (At. Mass of Fe = 56) .
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3.3. The density of copper metal is 8.95 g/cc, if the radius of Cu atom is 127.8 pm , is the Cu unit cell
simple Cubic, bcc or fcc ?
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3.4 Silver crystallises in fcc structure if the edge length of the unit cell is 4.07 x 10 -8 cm & density of the
crystal is 10.5 g/cc , calculate the atomic mass of Silver.
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3.5. Niobium (Nb) crystallises in bcc structure . If its density is 8.55 g/cc, calculate the atomic radius of
Nb. (atomic mass of Nb = 93 u)
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3.6. The well known mineral fluorite is chemically calcium fluoride . It is known that in one unit cell of
this mineral there are 4 Ca2+ ions and 8F ─ ions and that Ca2+ ions are arranged in fcc lattice . The F ─
ions fill all the tetrahedral holes in the fcc lattice of Ca2+ ions The edge of unit cell is 5.46 x 10 -8
cm in length the density of solid is 3.18 g/cc. Use this information to calculate the Avagadro’s
number . (Molar mass of CaF2 = 78.08 g/mol)
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3.7. Aluminium crystallises in a cubic close-packed structure. Radius of the atom in the metal is 125 pm .
(i) What is the length of the side of the unit cell ?
(ii) How many unit cells are present in 1 cm3 of Aluminium ?
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3.7. Sodium crystallises in a bcc unit cell .calculate the approximate No. of unit cells in 9.2 g of Sodium.
HOTS QUESTIONS
1. When a crystal of NaCl is heated in sodium vapour, it acquires a yellow colour. The yellow colour is due
to non stoichiometric defect. Name the defect.
2. In the face centered cubic arrangement of A and B atoms where A atoms are at the corner of the unit
cell and B atoms at the face centres. One of the A atom is missing from one corner in the unit cell.
What is the simplest formula of the compound?
3. In Chromium(III) Chloride, CrCl3, chloride ions have cubic close packed arrangement and Cr(III) ions are
present in the octahedral holes. What is the fraction of octahedral holes occupied? What is the fraction
of total number of holes occupied?
4. The composition of a sample of wustite is Fe0.93O1.00. What percentage of Fe is present as Fe(III)?
5. Calcium crystallizes in a face centred cubic unit cell with a=0.556nm. Calculate the density if
i. It contains 0.1% Frenkel defects.
ii. It contains 0.1% Schottky defects.
Hint:
Frenkel defect does not affect density.
d=zM/a3NA
Schottky defect reduces the density by 0.1%, assuming that volume remains constant.
d’=d( 1- 0.1/100)
;
d’=0.999d
6. The concentration of cation vacancies in NaCl crystal doped with CdCl2 is found to be 6.02x1016 mol-1.
What is the concentration of CdCl2 added to it?
7. Iron changes its crystal structure from body centred to cubic close packed structure when heated to
916°C. Calculate the ratio of the density of the BCC crystal to that of CCP crystal. Assume that the
metallic radius of the atom does not change.
Hint:
Volume same, so ratio of density is also same i.e. d(bcc)/d(ccp)
VALUE BASED QUESTION
1. Chetan asked his father, ‘’ How should a relationship be ? ‘’ His father gave him a piece of solid Iron
and said that the relationship should be like this. After reading this passage, answer the following
questions.
(i) Why do solids have a definite shape and a definite volume ?
(ii) Mention the values associated with the above conversion.
2. Solids have fixed shape and volume but experimentally it has been observed that solids are also
defective. Two types of defects are found in solids, namely, point defect and line defect. After
reading the above passage, answer the following questions(i) What type of defect can arise when a solid is heated ?
(ii) How many types of point defects are there ?
(iii) Mention the values associated with the above information.