Solids

Question 1

What are crystalline solids

Answer 1

solids in which particles are arranged in regular 3D order

Question 2

What are properties of solids

Answer 2

1. symmetry
2. definite geometrical shape
3. high melting point
4. break along cleavage plane (weak areas within crystal)

Question 3

What is habit of a crystal

Answer 3

the shape in which a crystal usually grows

Question 4

What conditions give large crystals

Answer 4

slow growth from slightly super-saturated sol or slowly cooling the solution

Question 5

What kind of crystals can NACl form

Answer 5

cubic when pure, flat or needle like when 10% urea present

Question 6

What is anisotropy

Answer 6

the property that shows diff intensity of physical properties in diff directions
1. AgI coefficient of expansion is positive in one direction and negative in other
2. electrical conductivity of graphite is better parallel than perpendicular

Question 7

What is isomorphism

Answer 7

crystals with same crystalline shape

Question 8

Name their crystalline form:
1. NaF and MgO (1:1 and 1:1)
2. KNO3 and NaNO3 (1:1:3 and 1:1:3)
3. ZnO and CdS (1:1 and 1:1)

Answer 8

1. cubic
2. rhombohedral
3. hexagonal

Question 9

What is polymorphism

Answer 9

occurrence of crystalline substance in more than one form

Question 10

Name crystalline forms of following:
1. AgNO3
2. CaCO3
3. KNO3

Answer 10

1. rhombohedral and orthorhombic
2. trigonal and orthorhombic
3. rhombohedral and orthorhombic

Question 11

What are allotropes of sulfur

Answer 11

amorphous is plastic and crystalline is rhombic sulfur (alpha) and monoclinic sulfur (beta)

Question 12

What are allotropes of oxygen

Answer 12

oxygen and ozone (O3)

Question 13

What is transition temp

Answer 13

temp at which crystal changes shape

Question 14

What is transition temp of rhombic to monoclinic sulfur

Answer 14

95.6

Question 15

What is transition temp of cubic tin to tetragonal

Answer 15

13.2

Question 16

What is transition temp of rhombohedral KNO3 to orthorhombic

Answer 16

128.5

Question 17

What factors affect shape of ionic solid

Answer 17

1. electrostatic forces of attraction
2. radius ratio
3. temp
4. impurities

Question 18

What is the coordination number and structure of following
1.< 0.155
2. 0.155-0.225
3. 0.225-0.414
4. 0.414-0.732
5. 0.732-1

Answer 18

a. 2 and linear (unstable)
b. 3 and triangular planar (unstable)
c. 4 and tetrahedral (ZnS and CuCl2)
d. 6 octahedral (NaCl and MgO)
e. 8 cubic (CsCl)

Question 19

What is effect of temp

Answer 19

cooling at slow rate makes perfect crystal

Question 20

What is effect of impurity

Answer 20

crystal will have defects

Question 21

What are examples of molecular solids

Answer 21

I2, P4, S8

Question 22

Most molecular solids melt under ______degrees

Answer 22

200

Question 23

what are noble gases, sulfur, iodine, phosphorus

Answer 23

non polar

Question 24

What are ice and sugar

Answer 24

polar

Question 25

What are properties of molecular solids

Answer 25

1. weak forces (Vanderwaals) 2.soft 3. low melting points

Question 26

What are three types of cubic unit cells

Answer 26

1. simple cubic lattice (cubic p-type) : point at only the edges of cube 2. body centred cubic (cubic i): point at edges and centre 3. face centred (cubic f): point at centre, edges and centre of each face of cube

Question 27

what is coordination number of each ion in NaCl

Answer 27

6

Question 28

What cube centred arrangement and shape does NaCl have

Answer 28

face centred and octahedral

Question 29

What is distance between two adjacent ions of diff type

Answer 29

2.815 Angstrom

Question 30

What is sum of ionic radius in NaCl

Answer 30

2.76 angstrom

Question 31

What does isomorphism depend on

Answer 31

1. no of atoms 2. combination of atoms