Which of the following statement regarding defect is correct.

• Due to Schottky defect, the density of crystalline solid decreases.

• Due to Frenkel defect, the density of crystalline solid decreases.

• Due to Schottky defect, entropy of solid decreases.

• Due to Frenkel defect, entropy of solid decreases.

462.

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

• pyroelectricity

• ferroelectricity

• piezoelectricity

• ferrielectricity

Frenkel and Schottky defects are

• nucleus defects

• non-crystal defects

• crystal defects

• nuclear defects

In the crystal of CsCl, the co-ordination number changes from 8:8 to 6:6 by:

• applying high pressure

• applying low temperature

• applying high temperature

• applying low pressure

A compound CuCl has face-centred cubic structure. Its density is 3.4 g cm^-3 , The length of unit cell is:

• 8.734 $\stackrel{0}{\mathrm{A}}$

• 5.834 $\stackrel{0}{\mathrm{A}}$

• 5.783 $\stackrel{0}{\mathrm{A}}$

• 8.153 $\stackrel{0}{\mathrm{A}}$

If the positions of Na⁺ and Cl^- are interchanged in NaCl , the crystal lattice with respect to Na⁺ and CI^- is:

• bcc and fcc

• fcc and bcc

• both fcc

• both bcc

The crystal with metal deficiency defect is :

• NaCl

• FeO

• KCl

• ZnO

ZnO is white when cold and yellow when heated. It is due to the development of

• Frenkel defect

• metal excess defect

• Schottky defect

• metal deficiency defect.

Among the following, the compound that is both paramagnetic and coloured is

• K₂Cr₂O₇

• (NH₄)₂[TiCl₆]

• VOSO₄

• K₃[Cu(CN)₄]

If an atom crystallises in bee lattice with r= 4 Å then the edge length will be

• 2 Å

• 8 Å

• 2.39 Å

• 9.23 Å