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1) In the normal spinel structure, the oxide ions are arranged in CCP pattern. The Zn2+ ions

occupy one eighth of the tetrahedral holes and one half of the octahedral voids are
occupied by Al3+. Give the formula of the spinel.
2) Metallic gold crystallizes in FCC lattice. How many nearest neighbours do each gold atom has?
3) 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.
4) 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?
5) For the structure given below identify the site marked as S.
6) In BCC lattice, what are the numbers of the nearest and next nearest neighbours?
7) What type of magnetism is shown by the substance whose magnetic moments are aligned as
given below:
99;9;99
8) A solid ‘X’ conducts electricity in solid state as well as in molten state. Its conductance
decreases with increase in temperature. Identify the solid X.
9) 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?
10) A compound AB crystallizes in BCC lattice with unit cell edge length of 480Pm.
If the radius of B is 225Pm. Calculate the radius of A+.
11) In the close packing arrangement of atoms does a face centred atom touch the face centred
atom of an adjacent face? Give reason for your answer.
12) Identify the crystal systems which have the following crystallographic dimensions:
aEc .===90°
a=bF.==90° =120°
13) Identify the unit cell and calculate the number of atoms per unit cell.
14)
a. What are the types of close packing shown in figure 1 and 2?
b. Write one example for each type of close packing in metals.
15) The composition of a sample of wustite is Fe0.93O1.00. What percentage of Fe is present as
Fe(III)?
16) 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.
17) A compound forms hexagonal close packed structure. What is the total number of voids in 0.5
mol of it? How many of these are tetrahedral voids?
18) The electrical conductivity of Zinc oxide increases on heating. Give reason.
19) Both the ionic solids NaF and MgO have the same number of electrons and about the same
inter nuclear distances. But the melting point of NaF is 992°C and that of MgO is 2642°C. Give
plausible reason for this observation.
20) 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?
21) 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
22) You are given marbles of diameter 10mm. They are to be placed such that their centres are
lying in a square bound by four lines each of length 40mm. What will be the arrangements of
the marbles in a plane so that maximum number of marbles can be placed inside the area?
Sketch the diagram and calculate the number of spheres per unit area.
23)
i. Name the defect shown in the figure.
ii. How does it affects the density of the solid
iii. Name a solid which shows this defect.
24) In the mineral, spinel, having the formula MgAl2O4, oxide irons are arranged in the cubic
close packing. Mg2+ions occupy the tetrahedral voids while Al3+ions occupy the octahedral
voids.
(i) What is the percentage of tetrahedral voids occupied by Mg2+ions?
(ii) What is the percentage of octahedral voids occupied by Al3+ions?
25) Metallic magnesium has a hexagonal close packed structure and has a density 1.74g cm-
Assuming magnesium atoms to be spherical, calculate the radius of magnesium atom.
(Atomic mass of Magnesium= 24.3).
Hints: Consider 1cm3 Mg and calculate mass of 1cm3 of Mg. Then calculate the No: of atoms
in that much mass of Mg. Calculate the volume occupied by the Mg Atoms and that occupied
E  0J DWRP 7KHQ XVLQJ WKH IRUPXOD ŒU
3 radius of Mg, r can be calculated
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