Molecular crystals exist in:

(1) crystalline state

(2) amorphous state

(3) non-crystalline state

(4) none of these

 

(A) 1,2,3

(B) 4

(C)1,2

(D) 2,3

The correct statement (s) regarding defects in solids is (are):

(a) Frenkel defect is usually favoured by a very small difference in the sizes of cation and anion

(b) Frenkel defect is a dislocation defect 

(c) Trapping of an electron in the lattice leads to the formation of F-centre

(d) Schottky defects have no effect on the physical properties of solids.

(1) b, c

(2) a, c

(3) c, d

(4) all

ln NaCl, the chloride ions occupy the space in a Fashion of 

1. BCC

2. FCC

3. Both 

4. None of the above 

Which of the following statements is/are correct?

(1) The co-ordination number of each type of ion in CsCl crystal is8

(2) A metal that crystallizes in bcc structure has coordination number of 12

(3) A unit cell of an ionic crystal shares some of its ions with other unit cells

(4) The length of the unit cell in NaCl is 552 pm($(r_{Na}^{+}=95pm;<mspace\; width="1em"></mspace>r_{Cl}^{-}=181<mspace\; width="1em"></mspace>pm)$

(A) 1, 3,4

(B) 1, 2,3

(C) 2, 3, 4

(D) ALL

Which is/are amorphous solid(s) ?

(1) NaCl

(2) CaF${}_2$

(3) Glass

(4) Daimond  

Which of the following is/are covalent solid(s)?

(1) Fe

(2) Diamond

(3) NaCl

(4) Graphite

A) 2, 4

B) 1, 3

C) 1, 2

D) ALL

The elements of symmetry in a crystal is/are:

1. plane of symmetry

2. axis of symmetry

3. centre of symmetry 

(1) 1, 2, 3

(2) 1, 2

(3) 2, 3

(4) NONE

Bragg's law is given by the equation:

(1) $n\lambda =2\theta <mspace\; width="1em"></mspace>\sin <mspace\; width="1em"></mspace>\theta$

(2) $n\lambda =2d<mspace\; width="1em"></mspace>\sin <mspace\; width="1em"></mspace>\theta$

(3) $2n\lambda =d<mspace\; width="1em"></mspace>\sin <mspace\; width="1em"></mspace>\theta$

(4) $\lambda =(2d/n)<mspace\; width="1em"></mspace>\sin <mspace\; width="1em"></mspace>\theta$

A metallic element crystalliese into lattics containing a sequence of layers of ABABABAB .... Any packing of spheres leaves out void in the lattice. The empty space in percentage by volume in this lattics is :

(1) 26%

(2) 32%

(3) 20%

(4) 30%

Perentages of free space in cubic close packed structure  and in body centred packed structure are respectively:

(1) 48% and 26%

(2) 30% and 26%

(3) 26% and 32%

(4) 32% and 48%