For fcc if AB is just like the rock salt like structure then, A⁺ and B^– are located at –

A⁺ - Tetrahedral voids ; B^- - Corner
A⁺ - Corner and faces ; B^- - Octahedral voids
A⁺ - Octahedral voids ; B^- - Corner and faces
A⁺ - Corner and faces ; B^- - Octahedral and tetrahedral voids

Solution

AB is just like NaCl. Thus twelve A⁺ are at edges and 1 within body of fcci.e. in octahedral voids and six B^- at faces and 8 at corner.

Na and Mg crystallize in the bcc and fcc type crystals respectively, then the number of atoms of Na and Mg present in the unit cell of their respective crystal is :

4 and 2
9 and 14
14 and 9
2 and 4

Solution

The pure crystalline substance on being heated gradually first forms a turbid liquid at constant temperature and still at higher temperature turbidity completely disappears. The behaviour is a characteristic of substance forming

Allotropic
Liquid
Isomeric
Isomorphous

Solution

Liquid crystals on heating first become turbid and then clear.

An example of a covalent crystalline solid is:

Solution

Si is an example of covalent crystalline solid among the given choices. Si atoms are covalently linked in tetrahedral manner.

Solid CH₄ is

ionic solid
covalent solid
molecular solid
does not exist

Solution

Solid CH₄ is a molecular solid. In this, the constituent molecules are held together by van der Waal’s forces

A solid with high electrical and thermal conductivity is

Si
Li
NaCl
Ice

Solution

Out of the given substances, only Li has high electrical and thermal conductivity as Li is a metallic solid.

Certain crystals produce electric signals on application of pressure. This phenomenon is called :

pyroelectricity
ferroelectricity
piezoelectricity
ferrielectricity

Solution

The phenomenon is called piezoelectricity.

Most crystals show good cleavage because their atoms, ions or molecules are

weakly bonded together
strongly bonded together
spherically symmetrical
arranged in planes

Solution

Crystals show good cleavage because their constituent particles are arranged in planes.

Which of the following compounds is a good conductor of electricity in solution state ?

Covalent
Molecular
Metallic
Ionic

Solution

Ionic compounds are dissociated in solution state and form ions. Ions are good carrier of charge which make solution conducting.

Frenkel and Schottky defects are :

nucleus defects
non-crystal defects
crystal defects
nuclear defects

Solution

Frenkel and Schottky defects are crystal defects. It arises due to dislodgement of cation or anion from their places in the crystal lattice.

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