In an f.c.c. unit cell, atoms are numbered as shown below. The atoms not touching each other are (Atom numbered 3 is face centre of front face).

(A) 3 & 4                                               

(B) 1 & 3 

(C) 1 & 2                                               

(D) 2 & 4

A metal crystallizes in two cubic phases, face centred cubic (fcc) and body centred cubic (bcc) whose unit cell length are 3.5 and 3.0 Å respectively. Calculate the ratio of density of fcc and bcc. 

(1) 2.123                                     

 (2) 1.259

(3) 5.124                                       

(4) 3.134

Triclinic crystal has the following unit cell parameters:

1. a = b = c; $\mathrm{\alpha }$ = $\mathrm{\beta }$ = $\mathrm{\gamma }$ = 90°

2. a = b $\ne$ c; $\mathrm{\alpha }$ = $\mathrm{\beta }$ = $\mathrm{\gamma }$ = 90°

3. a $\ne$ b $\ne$ c; $\mathrm{\alpha }$ $\ne$ $\mathrm{\beta }$ $\ne$ $\mathrm{\gamma }$ $\ne$ 90°

4. a = b $\ne$ c; $\mathrm{\alpha }$ = $\mathrm{\beta }$ = 90°, $\mathrm{\gamma }$ = 120°

An element X (At. Wt = 80 g/mol) having fcc structure, calculate no. of unit cells in 8 gm of X:

1. 0.4 X ${\mathrm{N}}_{\mathrm{A}}$

2. 0.1 X ${\mathrm{N}}_{\mathrm{A}}$

3. 4 X ${\mathrm{N}}_{\mathrm{A}}$

4. None of these

Which of the following defects does the KBr show?

1. Frenkel

2. Schottky

3. Metal excess

4. Metal deficiency

The composition of a sample of Wusitite is ${\mathrm{Fe}}_{0.93}\mathrm{O}$. What is the percentage of the iron present as ${\mathrm{Fe}}^{3+}$ in total iron?

1. 15.05%

2. 25%

3. 35%

4. 45%

KCl crystallizes in the same type of lattice as does NaCl. Given that ${{\mathrm{r}}_{\mathrm{Na}}}^{+}/{{\mathrm{r}}_{\mathrm{cl}}}^{-}$ = 0.50 and ${{\mathrm{r}}_{\mathrm{Na}}}^{+}/{{\mathrm{r}}_{\mathrm{k}}}^{+}$ = 0.70, calculate the ratio of the side of the unit cell for KCI to that for Nacl:

1. 1.143

2. 1.224

3. 1.414

4. 0.875

In a face centred cubic arrangement of metallic atoms, what is the relative ratio of the sizes of tetrahedral and octahedral voids ?

(1) 0.543                                   

(2) 0.732

(3) 0.414                                   

(4) 0.637

Close packing is maximum in the crystal which is-

(1) Simple cube                               

(2) bcc

(3) fcc                                             

(4) None

The n of a cubic unit cell is 4. The type of cell as-

(1) Body centred                               

(2) Face centred

(3) Primitive                                     

(4) None of these