Question 1
Why are solids rigid?

Question 2
Why do solids have a definite volume?

Question 3
Classify the following as amorphous or crystalline solids:
Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Question 4
Why is glass considered a super cooled liquid?

Question 5
Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?

Question 6
Classify the following solids in different categories based on the nature of intermolecular forces operating in them:
Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide.

Question 7
Solid A is a very hard electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?

Question 9
What type of solids are electrical conductors, malleable and ductile?

Question 14
What is the two dimensional coordination number of a molecule in square close packed layer?

Question 15
A compound forms hexagonal close-packed structure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids?

Question 16
A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3^rd of tetrahedral voids. What is the formula of the compound?

Question 17
Which of the following lattices has the highest packing efficiency
(i) simple cubic
(ii) body-centred cubic and
(iii) hexagonal close-packed lattice?

Question 18
An element with molar mass 2.7 x 10^-2kg mol^-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 x 10³ kg m^-3, what is the nature of the cubic unit cell?

Question 19
What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?

Question 20
What type of stoichiometric defect is shown by:
(i) ZnS
(ii) AgBr

Question 23
A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong?

Exercise 2
Question 2
What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

Exercise 2
Question 4
(i) What is meant by the term 'coordination number'?
(ii) What is the coordination number of atoms:
(a) in a cubic close-packed structure?
(b) in a body-centred cubic structure?

Exercise 2
Question 5
How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell? Explain.

Exercise 2
Question 6
'Stability of a crystal is reflected in themagnitude of its melting point'. Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?

Exercise 2

Question 7
How will you distinguish between the following pairs of terms:
(i) Hexagonal close-packing and cubic close-packing?
(ii) Crystal lattice and unit cell?
(iii) Tetrahedral void and octahedral void?

Exercise 2

Question 8
How many lattice points are there in one unit cell of each of the following lattice?
(i) Face-centred cubic
(ii) Face-centred tetragonal
(iii) Body-centred

Exercise 2

Question 12
A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?

Exercise 2
Question 16
Analysis shows that nickel oxide has the formula Ni_0.98 O_1.00. What fractions of nickel exist as Ni²⁺and Ni³⁺ions?

Exercise 2
Question 17
What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.

Exercise 2
Question 18
Non-stoichiometric cuprous oxide, Cu₂O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?

Exercise2 
Question 20
Classify each of the following as being either a p-type or an n-type semiconductor:
(i) Ge doped with In
(ii) B doped with Si.

Exercise 2
Question 21
Gold (atomic radius = 0.144 nm) crystallises in a face-centred unit cell. What is the length of a side of the cell?

Exercise 2
Question 22
In terms of band theory, what is the difference
(i) Between a conductor and an insulator
(ii) Between a conductor and a semiconductor

Exercise 2
Question 23
Explain the following terms with suitable examples:
(i) Schottky defect
(ii) Frenkel defect
(iii) Interstitials and
(iv) F-centres

Exercise 2
Question 24
Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm.
(i) What is the length of the side of the unit cell?
(ii) How many unit cells are there in 1.00 cm3of aluminium?

Exercise 2
Question 25
If NaCl is doped with 10^-3mol % of SrCl₂, what is the concentration of cation vacancies?

Exercise 2
Question 26
Explain the following with suitable examples:
(i) Ferromagnetism
(ii)Paramagnetism
(iii)Ferrimagnetism
(iv)Antiferromagnetism
(v)12-16 and 13-15 group compounds.