A crystal formula $A{B}_3$ has A ions at the cube corners and B ions at the edge centers. The coordination numbers of A and B are respectively 

(1) 6 and 6                                                 

(2) 2 and 6

(3) 6 and 2                                                 

(4) 8 and 8

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

Assertion :  The stability of a crystal gets reflected in its melting point.

Reason :  The stability of a crystal depends upon the strength of the interparticle attractive force. The melting point of a solid depends on the strength of the attractive force acting between the constitutent particles.

Assertion :  The melting point decreases in the order.
Water > ethyl alcohol > diethylether > methane

Reason : The strength of the intermolecular forces between these molecules follow the order
Water > ethyl alcohol > diethylether > methane

A rhombohedral unit cell is shown. What is its volume ?
Side length = a Å.

(1) $\frac{a^3}{\sqrt{3}}$                               

(2) $a^3\frac{\sqrt{3}}{2}$

(3) $\frac{a^3}{\sqrt{2}}$                             

(4) $a^3 \sqrt{\frac{3}{2}}$

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

Bragg’s equation is-

(1) $n\lambda =2\theta \sin \theta$                               

(2) $n\lambda =2d\sin \theta$

(3) $2n\lambda =d\sin \theta$                               

(4) $\lambda =\left(2d/n\right)\sin \theta$

Among the following types of voids, which one is the largest void-

(1) Triangular system                             

(2) Tetragonal system

(3) Monoclinic system                             

(4) Octahedral