The property of crystalline solid is not

1

(a)

anisotropic

(b)

isotropic

(c)

hard

(d)

dense

In a tetragonal crystal

1

(a)

\(a=b=c,\alpha =\beta ={ 90 }^{ ° }\neq \gamma \)

(b)

\(\alpha =\beta =\gamma ={ 90 }^{ ° },a=b\neq c\)

(c)

\(\alpha =\beta =\gamma ={ 90 }^{ ° },a\neq b\neq c\)

(d)

\(\alpha =\beta ={ 90 }^{ ° }\gamma ={ 120 }^{ ° },a=b\neq c\)

The number of octahedral sites per sphere in fcc structure is

1

(a)

8

(b)

4

(c)

2

(d)

1

In crystal structure of NaCl, total number of Cl^- ions in a unit cell is

1

(a)

6

(b)

4

(c)

8

(d)

2

Which of the following exists as covalent crystals in the solid state?

1

(a)

Phosphorus

(b)

Iodine

(c)

Silicon

(d)

Sulphur

Which of the following statement about amorphous solids is incorrect?

1

(a)

They melt over a range of temperature

(b)

They are anisotropic

(c)

There is no orderly arrangement of particles

(d)

They are rigid and incompressible

The vacant space in bcc lattice unit cell is

1

(a)

23%

(b)

32%

(c)

26%

(d)

48%

The packing efficiency of the two-dimensional square unit cell shown below is 

1

(a)

39.27%

(b)

68.02%

(c)

74.05%

(d)

78.54%

A compound M_pX_q has cubic close packing(ccp) arrangement of X.Its unit cell structure is shown below.The empirical formula of the compound is

1

(a)

MX

(b)

MX₂

(c)

M₂X

(d)

M₅X₁₄

In an ionic compound A⁺X^-,the radii of A⁺ and X^- ions are 1.0pm and 2.0pm respectively.The volume of the unit cell of the crystal AX will be

1

(a)

27pm³

(b)

64pm³

(c)

125pm³

(d)

216pm³

Conductivity of silicon increases on doping it with phosphorus. Why

1

(a)

It is because it forms n-type semiconductor in which electrons are free to move.

A solid with cubic crystal is made of two elements 'P' and 'Q'. Atoms of 'Q' are at the corners of the cube and 'P' at body centre. What is formula of compound?

1

(a)

\(Q=8\times \frac { 1 }{ 8 } =1, \ P=1\) 
\(\therefore\) Formula of compound is PQ.

A cubic solid is made of two elements X and Y. Atoms Y are at the corners of the cube and X at the body centre. What is the formula of the compound?

1

(a)

\(Y=8\times \frac { 1 }{ 8 } =1;X=1,\) \(\therefore \) Formula is XY.

How many atoms can be assigned to its unit cell if an element forms
(i) a body-centred cubic cell, and
(ii) a face-centred cubic cell?

1

(a)

(i) Z = 2 for bcc element
(ii) Z = 4 for fcc element

Why is glass considered as supercooled liquid?

1

(a)

It is because glass windows are thicker at the bottom and thinner at the top. it shows that glass can flow, that is why it is called super cooled liquid.

What types of solids are electrical conductors, malleable and ductile?

1

(a)

Metallic solids are electrical conductors, malleable and ductile.

What is the two dimensional coordination number of a molecule in square close-packed layer?

1

(a)

Four

Name the non-stoichiometric point defect responsible for colour in alkali halides.

1

(a)

Metal excess defect: Excessof metal ions and formation of F-centre due to trapped electrons are responsible for colour in alkali halides.

Name an element with which silicon can be doped to give a p-type semiconductor.

1

(a)

Silicon doped with Gallium will be p-type semiconductor.

Name the crystal defect which lowers the density of an ionic crystal.

1

(a)

Schottky defect.

What makes the crystal of KCI appear sometimes violet?

1

(a)

It is due to presence of F-centre. Electrons present at the site of anion forming f-centre absorb ligh form visible region and radiate complementary colour.

What is the effect of Schottky and Frenkel defects on the crystaline solids?

1

(a)

The density decreases in the case of Schottky defect, whereas it remain the same in the case of Frenkel defect.

Copper is conducting as such will copper sulphate is conducting only in molten state or in aqueous solution. Why

1

(a)

Copper is a conductor because it has free electrons to move, where as CuSO₄ conducts electricity in molten state because ions become free to move in molten state or in aqueous solution but not in solid state.

What is the maximum possible coordination number of an element ?

1

(a)

12

Name an element with which germanium can be doped to produce an n-type semiconductor.

1

(a)

Arsenic