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When heated above 916$°$C, iron changes its bcc crystalline form to fcc without the change in the radius of atom. The ratio of atom. The ratio of density of the crystal before heating and after heating is :
1. 1.069
2. 0.918
3. 0.725
4. 1.231

In an atomic bcc, what fraction of edge is not covered by atoms ?
1. 0.32
2. 0.16
3. 0.134
4. 0.268

Sodium (Na = 23) crystallizes in a bcc arrangement with the interfacial separation between the atoms at the edge 53.6 pm. The density of sodium crystal is :
1. 2.07 g/cc
2. 2.46 g/cc
3. 1.19 g/cc
4. none of these

The density of solid argon (Ar = 40) g/mol is 1.68 g/ml at 40 K. If the argon atom is assumed to be a sphere of radius $1.50\times {10}^{-8}$ cm, what % of solid Ar is apparently empty space ?
1. 35.64
2. 64.36
3. 74 %
4. none of these

First three nearest neighbour distances for primitive cubic lattice are respectively (edge length of unit cell = a):
1. $\mathrm{a},\sqrt{2}\mathrm{a},\sqrt{3}\mathrm{a}$
2. $\sqrt{3}a,\sqrt{2}a,a$
3. $\mathrm{a},\sqrt{2}\mathrm{a},2\mathrm{a}$
4. $\mathrm{a},\sqrt{3}\mathrm{a},2\mathrm{a}$

In a planar tera-atomic molecule, ${\mathrm{XY}}_3$, X is at the centroid of the equilateral triangle formed by the atoms, Y. If X-Y bond distance is 1 $\stackrel{\mathrm{o}}{\mathrm{A}}$, what is the distance between the centres of any two atoms ?
1. 1/$\sqrt{3}$ $\stackrel{\mathrm{o}}{\mathrm{A}}$
2. $\sqrt{2}$ $\stackrel{\mathrm{o}}{\mathrm{A}}$ 
3. $\sqrt{3}$ $\stackrel{\mathrm{o}}{\mathrm{A}}$ 
4. 1/$\sqrt{2}$ $\stackrel{\mathrm{o}}{\mathrm{A}}$

The distance between an octahedral and tetrahedral void in fcc lattice would be :
1. $\sqrt{3}$a
2. $\frac{\sqrt{3}}{2}a$
3. $\frac{\sqrt{3}}{3}a$
4. $\frac{\sqrt{3}}{4}a$

An element X(At. wt = 80 g/mol having fcc structure, calculate no. of unit cells in 8 gm of X;
1. $0.4\times {\mathrm{N}}_{\mathrm{A}}$
2. $0.1\times {\mathrm{N}}_{\mathrm{A}}$
3. $4\times {\mathrm{N}}_{\mathrm{A}}$
4. None of these

Molybdenum (At. wt = 96 $\mathrm{g} {\mathrm{mol}}^{-1}$) crystallizes as bcc crystal. If density of crystal is 10.3 g/cm³ , then radius of Mo atom is ( use ${\mathrm{N}}_{\mathrm{A}}=6\times {10}^{23}$) ;
1. 111 pm
2. 314 pm
3. 135.96 pm
4. None of these

The atomic radius of strontium (sr) is 215 pm and it crystallizes with closest cubic packing. Edge length of the cube is :
1. 430 pm
2. 608.2 pm
3. 496.53 pm
4. none of these

By X-ray diffraction it is found that Ni (at mass = 59 g mol^-1), crystallizes with ccp. The edge length of the unit cell is is 3.5 $\stackrel{0}{\mathrm{A}}$. If density of Ni crysal is 9.0 g/cm³. Then value of Avogadro's number from the data is :
1. $6.05\times {10}^{23}$
2. $6.11\times {10}^{23}$
3. $6.02\times {10}^{23}$
4. $6.023\times {10}^{23}$

Which one of the following schemes of ordering closes packed sheets of equal sized spheres do not generate closed packed lattice ?
1. ABCABC
2. ABACABAC
3. ABBAABBA
4. ABCBCABCBC

In the spinel structrue, oxides ions are cubical-closest packed whereas 1/8th of tetrahedral voids are occupied by ${\mathrm{A}}^{2+}$ cation and 1/2 of octahedral voids are occupied by ${\mathrm{B}}^{3+}$ cations. The general formula of the compound having spinel structure is :
1. ${\mathrm{A}}_2{\mathrm{B}}_2{\mathrm{O}}_4$
2. ${\mathrm{AB}}_2{\mathrm{O}}_4$
3. ${\mathrm{A}}_2{\mathrm{B}}_4{\mathrm{O}}_2$
4. ${\mathrm{A}}_4{\mathrm{B}}_2{\mathrm{O}}_2$

An alloy of copper, silver and gold is found to have copper constituting the ccp lattice. If silver atoms occupy the edge centres and gold is present at body centre, the alloy will have the formula :
1. ${\mathrm{Cu}}_4{\mathrm{Ag}}_2\mathrm{Au}$
2. ${\mathrm{Cu}}_4{\mathrm{Ag}}_4\mathrm{Au}$
3. ${\mathrm{Cu}}_4{\mathrm{Ag}}_3\mathrm{Au}$
4. CuAgAu

An ionic compound AB has fluorite type structures. If the radius  ${\mathrm{B}}^{-}$ is 200 pm, then the ideal radius of ${\mathrm{A}}^{+}$ would be :
1. 82.8 pm
2. 146.4 pm
3. 40 om
4. 45 pm

CsCl has bcc structure with edge length 4.3 pm. The shortest inter ionic distance in between Cs⁺ and Br^- is :
1. 3.72 pm
2. 1.86 pm
3. 7.44 pm
4. 4.3 pm

When NaCl is doped with ${10}^{-5}$ mole % of ${\mathrm{SrCl}}_2$, what is the no. of cationic vacancies ?
1. ${10}^{-5}\times \hspace{0.17em}{\mathrm{N}}_{\mathrm{A}}$
2. ${10}^{-7}\times \hspace{0.17em}{\mathrm{N}}_{\mathrm{A}}$
3. $2\times {10}^{-7}\times \hspace{0.17em}{\mathrm{N}}_{\mathrm{A}}$
4. None of these

The composition of a sample of Wustite is ${\mathrm{Fe}}_{0.93}\mathrm{O}$. What is the percentage of iron present as ${\mathrm{Fe}}^{3+}$ in total iron ?
1. 15.05 %
2. 25 %
3. 35 %
4. 45 % 

A certain sample of cuprous sulphide is found to have composition ${\mathrm{Cu}}_{1.8}\mathrm{S}$, because of incorporation of ${\mathrm{Cu}}^{2+}$ ions in the lattice. What is the mole % of ${\mathrm{Cu}}^{2+}$ in total copper content in this crystal ?
1. 99.8 %
2. 11.11 %
3. 88.88 %
4. None of these

A certain sample of cuprous sulphide is found to have composition ${\mathrm{Cu}}_{1.8}\mathrm{S}$, because of incorporation of ${\mathrm{Cu}}^{2+}$ ions in the lattice. What is the mole % of ${\mathrm{Cu}}^{2+}$ in total copper content in this crystal ?
1. 99.8 %
2. 11.11 % 
3. 88.88 %
4. none of these