Chapter -1 The Solid State

what is chemical ?

(a) Explain the following phenomena with the help of Henry’s law.
(i) Painful condition known as bends.
(ii) Feeling of weakness and discomfort in breathing at high altitude.
(b) Why soda water bottle kept at room temperature fizzes on opening?

Why are aquatic species more comfortable in cold water in comparison to
warm water?

What is the significance of Henry’s Law constant KH?

Concentration terms such as mass percentage, ppm, mole fraction and molality
are independent of temperature, however molarity is a function of temperature.
Explain.

Explain the solubility rule “like dissolves like” in terms of intermolecular forces
that exist in solutions.

Explain why on addition of 1 mol of NaCl to 1 litre of water, the boiling point
of water increases, while addition of 1 mol of methyl alcohol to one litre of
water decreases its boiling point.

Components of a binary mixture of two liquids A and B were being separated
by distillation. After some time separation of components stopped and
composition of vapour phase became same as that of liquid phase. Both the
components started coming in the distillate. Explain why this happened.

How does the doping increase the conductivity of semiconductors?

Show that in a cubic close packed structure, eight tetrahedral voids are present
per unit cell.

With the help of a labelled diagram show that there are four octahedral voids
per unit cell in a cubic close packed structure.

Match the type of packing given in Column I with the items given in Column II.
Column I                                                           Column II
(i) Square close packing in                                      (a) Triangular voids
two dimensions
(ii) Hexagonal close packing                                    (b) Pattern of spheres is repeated in
in two dimensions every fourth layer
(iii) Hexagonal close packing in                                (c) Coordination number 4
three dimensions 
(iv) Cubic close packing in                                       (d) Pattern of sphere is repeated in
three dimensions alternate layers

Match the items given in Column I with the items given in Column II.
Column I                                                                 Column II
(i) Mg in solid state                                                   (a) p-Type semiconductor
(ii) MgCl2 in molten state                                            (b) n-Type semiconductor
(iii) Silicon with phosphorus                                          (c) Electrolytic conductors
(iv) Germanium with boron                                         (d) Electronic conductors

Match the type of unit cell given in Column I with the features given in
Column II.
Column I                                                     Column II
(i) Primitive cubic unit cell                        (a) Each of the three perpendicular
edges compulsorily have the different
edge length i.e; a≠b≠c.
(ii) Body centred cubic unit cell                    (b) Number of atoms per unit cell is one.
(iii) Face centred cubic unit cell                    (c) Each of the three perpendicular
edges compulsorily have the same
edge length i.e; a = b = c
(iv) End centred orthorhombic                        (d) In addition to the contribution from
unit cell the corner atoms the number of atoms
present in a unit cell is one.
                                                             (e) In addition to the contribution from
the corner atoms the number of
atoms present in a unit cell is three.

Note : In the following questions match the items given in Column I with
the items given in Column II. In some questions more than one item of
Column I and Column II may match.

 Match the defects given in Column I with the statements in given Column II.
Column                                                          I Column II
(i) Simple vacancy defect                                  (a) shown by non-ionic solids and
increases density of the solid.
(ii) Simple interstitial defect                            (b) shown by ionic solids and decreases
density of the solid.
(iii) Frenkel defect                                        (c) shown by non ionic solids and density
of the solid decreases
(iv) Schottky defect                                      (d) shown by ionic solids and density of
the solid remains the same.

Under which situations can an amorphous substance change to crystalline form?

In a compound, nitrogen atoms (N) make cubic close packed lattice and metal
atoms (M) occupy one-third of the tetrahedral voids present. Determine the
formula of the compound formed by M and N?

Explain why does conductivity of germanium crystals increase on doping
with galium.

Why does the electrical conductivity of semiconductors increase with rise in
temperature?

Why does white ZnO (s) becomes yellow upon heating?

Why is FeO (s) not formed in stoichiometric composition?

Why does table salt, NaCl, some times appear yellow in colour?

Inspite of long range order in the arrangement of particles why are the crystals
usually not perfect?

Why are solids incompressible?

Why are liquids and gases categorised as fluids?

What do you mean by paramagnetic substance?

Which substance exhibit schottky and Frenkel both defects. 

Name a salt which is added to Agcl so as to produce cation vacancies. 

Why Frenkel defects not found in pure Alkali metal halide. 

What is the use of amorphous silica? 

Analysis shows that a metal oxide has the empirical formula Mo.9801.00. Calculate the percentage of M2+ and M3+ ions in the crystal.

What is the co‐ordination no. of cation in Antifluorite structure? 

What is the Co.No. of cation and anion in Caesium Chloride. 

What is F centre?

How does amorphous silica differ from quartz?

Which point defect lowers the density of a crystal?

Why glass is called supper cooled liquids?

Some of the very old glass objects appear slightly milky instead of being transparent why?

What is anisotropy?

What is the coordination number of atoms?

a)   in fcc structure b) in bcc structure

 How many lattice points are there in one cell of ‐

a)   fcc b) bcc c) simple cubic

What are the co‐ordination numbers of octahedral voids and tetrahedral voids?

Why common salt is sometimes yellow instead of being of being pure white?

A compound is formed by two elements X and Y. The element Y forms ccp and atoms of X occupy octahedral voids. What is formula of the compound?

Explain how electrical neutrality is maintained in compounds showing Frenkel and Schottky defect.

Calculate the number of atoms in a cubic unit cell having one atom on each corner and two atoms on each body diagonal.

Gold crystallizes in an FCC unit cell. What is the length of a side of the cell(r=0.144mm)

Classify each of the following as either a p‐type or n‐type semi‐conductor. a) Ge doped with In

b) B doped with Si

In terms of band theory what is the difference between a conductor, an insulator and a semi‐

conductor?

CaCl2 will introduce Scotty defect if added to AgCl crystal. Explain

The electrical conductivity of a metal decreases with rise in temperature while that of a semi‐

conductor increases. Explain.

What  type  of   substances  would  make  better   permanent  magnets,  ferromagnetic  or ferromagnetic, why?

In a crystalline solid, the atoms A and B are arranged as follows:‐

a.   Atoms A are arranged in ccp array.

b.   Atoms B occupy all the octahedral voids and half of the tetrahedral voids. What is the

formula of the compound?

In compound atoms of element Y forms ccp lattice and those of element X occupy 2/3rd of tetrahedral voids. What is the formula of the compound?

Explain the following with suitable examples:

(i) Ferromagnetism

(ii)Paramagnetism

(iii)Ferrimagnetism

(iv)Antiferromagnetism

(v)12-16 and 13-15 group compounds.

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

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?

Explain the following terms with suitable examples:

(i) Schottky defect

(ii) Frenkel defect

(iii) Interstitials and

(iv) F-centres

In terms of band theory, what is the difference

(i) Between a conductor and an insulator

(ii) Between a conductor and a semiconductor

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

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.

Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

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?

What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism

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

Copper crystallises into a fcc lattice with edge length 3.61 x 10^-8cm. Show that the calculated density is in agreement with its measured value of 8.92 g cm^-3.

If the radius of the octachedral void is r and radius of the atoms in close packing is R, derive relation between r and R.

Niobium crystallises in body-centred cubic structure. If density is 8.55 g cm^-3, calculate atomic radius of niobium using its atomic mass 93 u.

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?

Silver crystallises in fcc lattice. If edge length of the cell is 4.07 x 10^-8cm and density is 10.5 g cm^-3, calculate the atomic mass of silver.

Calculate the efficiency of packing in case of a metal crystal for

(i) simple cubic

(ii) body-centred cubic

(iii) face-centred cubic (with the assumptions that atoms are touching each other).

Explain

(i) The basis of similarities and differences between metallic and ionic crystals.

(ii) Ionic solids are hard and brittle.

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

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?

'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?

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

(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?

Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous.

(i) Tetra phosphorus decoxide (P₄O₁₀) (vii) Graphite

(ii) Ammonium phosphate (NH₄)₃PO₄ (viii) Brass

(iii) SiC (ix) Rb

(iv) I₂ (x) LiBr

(v) P₄ (xi) Si

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

What type of substances would make better permanent magnets, ferromagnetic or ferrimagnetic. Justify your answer.

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?

Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

xplain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.

What type of stoichiometric defect is shown by:

(i) ZnS (ii) AgBr

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

An element with molar mass 2.7 x 10^-2kg mol^-1forms 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?

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

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

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?

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

Explain how much portion of an atom located at (i)corner and (ii)body-centre of a cubic unit cell is part of its neighbouring unit cell.

Distinguish between

(i)Hexagonal and monoclinic unit cells

(ii) Face-centred and end-centred unit cells.

Distinguish between

(i)Hexagonal and monoclinic unit cells

(ii) Face-centred and end-centred unit cells.

Name the parameters that characterize a unit cell.

Give the significance of a 'lattice point'.

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

Ionic solids conduct electricity in molten state but not in solid state. Explain.

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?

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.

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?

Why is glass considered a super cooled liquid?

Classify the following as amorphous or crystalline solids:

Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Why do solids have a definite volume?

Why are solids rigid?