The solid state chemistry class 12

S.No.	The solid state chemistry class 12
.	In text Questions
1.1	Why are solids rigid?
1.2	Why do solids have a definite volume?
1.3	Classify the following as amorphous or crystalline solids: Polyurethane,naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinylchloride, fibre glass, copper.
1.4	Why is glass considered a super cooled liquid?
1.5	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?
1.6	Classify the following solids in different categories based on the nature ofintermolecular forces operating in them:Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide,graphite, rubidium, argon, silicon carbide.
1.7	Solid A is a very hard electrical insulator in solid as well as in molten stateand melts at extremely high temperature. What type of solid is it?
1.8	Ionic solids conduct electricity in molten state but not in solid state. Explain.
1.9	What type of solids are electrical conductors, malleable and ductile?
1.10	Give the significance of a ‘lattice point’.
1.11	Name the parameters that characterise a unit cell.
1.12	Distinguish between (i) Hexagonal and monoclinic unit cells (ii) Face-centred and end-centred unit cells.
1.13	Explain how much portion of an atom located at (i) corner and (ii) bodycentreof a cubic unit cell is part of its neighbouring unit cell.
1.14	What is the two dimensional coordination number of a molecule insquare close-packed layer?
1.15	compound forms hexagonal close-packed structure. What is the totalnumber of voids in 0.5 mol of it? How many of these are tetrahedral voids?
1.16	A compound is formed by two elements M and N. The element Nforms ccp and atoms of M occupy 1/3rd of tetrahedral voids. Whatis the formula of the compound?
1.17	Which of the following lattices has the highest packing efficiency (i) simplecubic (ii) body-centred cubic and (iii) hexagonal close-packed lattice?
1.18	An element with molar mass 2.7×10-2 kg mol-1 forms a cubic unit cellwith edge length 405 pm. If its density is 2.7×103 kg-3, what is thenature of the cubic unit cell?
1.19	What type of defect can arise when a solid is heated? Which physicalproperty is affected by it and in what way?
1.20	What type of stoichiometric defect is shown by: (i) ZnS (ii) AgBr
1.21	Explain how vacancies are introduced in an ionic solid when a cationof higher valence is added as an impurity in it.
1.22	Ionic solids, which have anionic vacancies due to metal excess defect,develop colour. Explain with the help of a suitable example.
1.23	A group 14 element is to be converted into n-type semiconductor by dopingit with a suitable impurity. To which group should this impurity belong?
1.24	What type of substances would make better permanent magnets,ferromagnetic or ferrimagnetic. Justify your answer.
	Exercises - 1
1.1	Define the term 'amorphous'. Give a few examples of amorphous solids.
1.2	What makes a glass different from a solid such as quartz? Under whatconditions could quartz be converted into glass?
1.3	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(vi) Plastic
1.4	(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?
1.5	How can you determine the atomic mass of an unknown metal if you knowits density and the dimension of its unit cell? Explain.
1.6	'Stability of a crystal is reflected in the magnitude of its melting points'.Comment. Collect melting points of solid water, ethyl alcohol, diethyl etherand methane from a data book. What can you say about the intermolecularforces between these molecules?
1.7	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?
1.8	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
1.9	Explain (i) The basis of similarities and differences between metallic and ionic crystals. (ii) Ionic solids are hard and brittle.
1.10	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).
1.11	Silver crystallises in fcc lattice. If edge length of the cell is 4.07 × 10–8cm and density is 10.5 g cm–3, calculate the atomic mass of silver.
1.12	A cubic solid is made of two elements P and Q. Atoms of Q are at thecorners of the cube and P at the body-centre. What is the formula of thecompound? What are the coordination numbers of P and Q?
1.13	Niobium crystallises in body-centred cubic structure. If density is 8.55g cm–3, calculate atomic radius of niobium using its atomic mass 93 u.
1.14	If the radius of the octahedral void is r and radius of the atoms in closepackingis R, derive relation between r and R.
1.15	Copper crystallises into a fcc lattice with edge length 3.61 × 10–8 cm.Show that the calculated density is in agreement with its measuredvalue of 8.92 g cm–3
1.16	Analysis shows that nickel oxide has the formula Ni0.98O1.00. What fractionsof nickel exist as Ni2+ and Ni3+ ions?
1.17	What is a semiconductor? Describe the two main types of semiconductorsand contrast their conduction mechanism.
1.18	Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory.In this oxide, copper to oxygen ratio is slightly less than 2:1. Can youaccount for the fact that this substance is a p-type semiconductor?
1.19	Ferric oxide crystallises in a hexagonal close-packed array of oxide ionswith two out of every three octahedral holes occupied by ferric ions.Derive the formula of the ferric oxide.
1.20	Classify each of the following as being either a p-type or a n-type semiconductor: (i) Ge doped with In (ii) B doped with Si.
1.21	Gold (atomic radius = 0.144 nm) crystallises in a face-centred unit cell. What is the length of a side of the cell?
1.22	In terms of band theory, what is the difference (i) between a conductor and an insulator (ii) between a conductor and a semiconductor?
1.23	Explain the following terms with suitable examples: (i) Schottky defect (ii) Frenkel defect (iii) Interstitials and (iv) F-centres.
1.24	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 cm3 of aluminium?
1.25	If NaCl is doped with 10–3 mol % of SrCl2, what is the concentration of cation vacancies?
1.26	Explain the following with suitable examples: (i) Ferromagnetism (ii) Paramagnetism (iii) Ferrimagnetism (iv) Antiferromagnetism (v) 12-16 and 13-15 group compounds.

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