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1 CHPATER - SOLID STATE Very short answer questions,a6ol31^,rne)1t JVo'L Q.I Which stoichiometric defect in crystals increases the density of a solid? Q.2 Crystalline solids are anisotropic in nature. What does this statement mean? Q.3 What type of semiconductor is obtained when silicon is doped with arsenic? Q.4 What group 14 element is to be converted into n-type semiconductor by doping with a suitable impurity. To which group should this impurity belong? Q.5 What is primitive cell? Q.6 How many atoms are present per unit cell in a body centred cubic structure? Q.7 Why is Frenkel defect not found in pure alkali metal halides? Q.8 Name one ionic solid which shows Frenkel as well as Schottky defects. Q.9 What is the effect of temperature on the conductivity of metals and semi-conductors? Q.10 What are isotropic substances? Are crystalline substances isotropic? Q.1 I What is the nature of crystal defect produced when sodium chloride crystal is doped with mgcl? Q.12 What are ferromagrlqtic substances? Q.13 How may the condubtivity of an intrinsic semiconductor be increased? Q.14 What is the effect of presence of Schottky defects on the density of a crystal? What is the coordination number of each type of ion in a rock salt type crystal structure? Q.l5 Q.16 What is meant by'doping' in a semiconductor? Q.17 When atoms are placed at the corners of all 12 edges of a cube, how many atom! are present per unit cell? Q.18 What is an F-centre? Q.19What is the total number of atoms per unit cell in a face centred cubic (fcc) structure? Q.20A unit cell consists of a cube in which there are anions (Y) at each corner and cations (X) at the centre of alternate faces of the unit cell. What is the simplest formula of the compound? Q.21 Why does Frenkel defect not change the density of AgCl crystals? Q.22 Name a salt which is added to AgCl so as to produce cation vacancies. Q.23 What makes alkali metal halides sometimes coloured, which are otherwise colourless. Q.24 Mention one property which is caused due to the presence of F-centre in a solid. non-stoichiometric point responsible Q.25 Name the defect for colour in alkali metal halides. glass Q.26 Why is considered a super cooled liquid? would Q27 What type of substance make better permanent maganets, ferromagnetic or feromagnetic? Justify your answer. Q.28 What type of stoichiometric defect is shown by (i) ZnS (ii) AgBr? Define forbidden zone of an isulator. Q.29 Q.30 Refractive index of a soiid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property? Q.3l Name the (i) most symmetrical and (ii) most unsymmetrical crystal system. Q.32. The ions of NaF and MgO all have the same number of electrons and the internuclear distances are about the same (235pm and 215 pm). Why then are tho melting points of Naf and MgO so different (992C and2642 c)? Q.33 How are unit cell and space lattice related? Q.34 What are non-stoichiometric compounds? Give one example.

2 Q. 35 What are point defects? Q.36 What are n-type semiconductors? Q.37 Which point defect in crystals of solid does not change the density of the solid? Q.38 How do metallic and ionic substances differ in conduction electiricity? Q.39 What happens when feromagnetic FeO is heated at 850 K and why? Try Yourself 1. Which stoichiometric defect in crystals increases the density of a solid? 2. Define unit cell an space lattice. 3. Arrange simple cubic, body centred cubic, face centred cubic and hexagonal close packing in the increasing order of packing efficiency. 4. Which point defect in a crystal of a solid decreases the density of the solid? What tetrahedral hole octahedral 5. is the coordination number of an ion occupying (i) (ii) hole? 6. Why doe Li acquire pink colour when heated in litium vapurs? 7. Given the number of atoms per unit cell in Asimple curbic arrangement (i) (ii) Face centeied cubio amangement? (iii) Body centred cubic arrangement 8. What are non-stoichiometric compounds? Give one example. 9. Which of the two spheres-one occupying a tetrahedral site and the other one occupying octahedral site is larger in size? 10. What is the radius ratio for an ion to occupy a octahedral site? I 1. In a close packing of N-spheres, how many octahedral and tetrahedral sites are presentl 12. Which of the following are molecular solids? Solid CO2, SiC, ICI, Graphite. Short Answer Questions Q. I Distinguish between (i) Hexagonal and monoclinic unit cell. (ii) Face centred and end centred unit cell. Q.2 How would you account for the following? (i) Zi,nc oxide exhibits enhanced electrical conductivity on heating. (ii) The electrical conductivity of metals decreases with rise in temperature while that of a semiconductor increases. Q. 3 How many atoms can be assigned to its unit cell if an element forms, (a) face centred cubic cell (b) body centred cubic cell? Q. 4. Ferric oxide crystallizes in a hexagonal close packed array of oxide ions with two out of every three octahedral holes occupied by femic ions. Drive the formula of the ferric Q.5 Classify each of the following as being either a p-type or n-type semiconductor: (i) * Ge doped with In (ii) B doped with Si Q.6 Silver crystallizes in face centred cubic unit cell. Each side of the unit cell has a length of 409 pm. Calculate the radius of an atom of silver (assume that each face atom is touching four corner atoms). Q. 7 An element occurs in bcc structure with cell edge of 288 pm. Its density is 7.2 g cm. calculate the atomic mass of the element. {

3 Q.8 X-ray studies of silver crystals show that it forms ccp lattice and edge length of the unit cell is pm. Calculate the density of silver (atomic mass:107.9 u). Q.9 Calculate the packing efficiency of a metal crystal for a simple cubic unit cell. Q.10 Pure silicon is an insulator, silicon doped with phosphorous is a semi-conductor. Silicon doped with gallium is also a semiconductor. What is the difference between the two doped silicon semiconductors? Q.l 1 What are the important consequences of Schottky and Frenkel defects in crystals? Q.12 Iron has a body centred cubic unit cell with a cell edge of pm. the density of iron is 7.87 glc-3. use this information to calculate avogadros's number. Q.l3 Sodium crystallizes in abcc unit cell. Calculate the approximate number of unit cells in 9.2 g of sodium.( Atomic mass of Na:23u)-. Q. 14 Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it. Q. l5 Analysis shows that nickel oxide has formula Ni O. What fraction of nickel exist as Ni2* and Ni3* ions? Q.16 Non-stoichirometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ration is slightly less than 2:l- Can you account for the factthat this substance is a p-type semiconductor? Q.17 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? Q.18 Copper crystallizes into a fcc lattice with edge length 3.618*10-8 cm. calculate its density. t Q.19 Define the following terms: (i) ferromagnetism (ii) ferrimagnetis. Q. 20 Gold (atomic radius:0.144 nm) crystallizes in a face centered unit cell. What is the length of a side of the cell? Try yourself 1. Silver crystallizes in face-centered cubic unit cell. Each side of this unit has a length of 400 pm. Calculate the radius of the silver atom. (assume the atoms just touch each other on the diagonal across the face of the unit cell. That is each face atom is touching. 2. A compound formed by elements A and B crystallizes in the cubic arrangements in which A atoms arc at the corners of the cube B atoms are at the face centres. What is the formula of the compound? 3. In a solid 'AB', 'A' atoms have ccp arrangement and B atoms occupy all the octahedral sites. all the face atoms along one of the the If centered axes are removed, then what will be resultant stoichiometry of the compound? 4. The density of Cs Br which has a CsCl (bcc) structure is 4.4 glcm3. the unit cell edge length is 400 pm. Calculate the interionic distance in crystal of CsBr (N6:6.023*1023 mol atomic mass: Cs:133, Br:80). 5. How is ferromagnetic different form paramagnetism? 6. A compound is formed by two elements M and N. The element N forms ccp and M atoms occupy 1/3 of tetrahedral voids. What is the formula of the compound? 7. Silvercrystallizes in fcc lattice. If edge length ofthe cell is 4.077*10-8 cm and density is 10.5 glcm3. Calculate the atomic mass of silver.

4 8. Copper uystallizes into a fcc lattice with edge length 3.61*10-8 cm. Show that the calculate density is in agreement with its measured value of 8.92 gl". ' g. If NaCl is doped with 10-3 molyo of SrClz. What is the concentration of cation vacancies? packed with two out of 10. Ferric oxide crystallizes in a hexagonal close array of oxide ions every three octahedral holes occupied by ferric ions. Derive the formula of ferric oxide A cubic solid is made of two elements P and Q. Atoms of Q are the corners of the cube and P at the body- centre. What is the formula of the compound? What are the coordination numbersofp&q? I2.Atoms of element B form hcp lattice and those of the element A occupy 213'd of the tetrahedral voids. What is the formula of the compound formed by these elements A and B? 13.If three elements X,Y and Z crystallize in a cubic solid with X atoms at the corners, Y atom is the cube centres and Z atoms at the faces of the cube, then write the formula of the compound. 14. Explain each of the following with a suitable example: (i) Frenkel defect in crystals (ii) Paramagnetism 15. How do metallic and.ionic substances differ in conduction electricity? 16. How would you accoint for the following? (i) Impuity doped silicon is a semiconductor (ii) Schottky defect lowers the density of related solids. Short Answer Questions 1. Give important differences between crystalline and amorphous solids An element crystallizes in a structure having fcc unit cell of an edge 200 pm. Calculate its density if 2O0 g of this element contains 24*7023 atoms. t 3. The density of lead is gl"*'and the metal crystallizes in fcc unit cell. Estimate the radius of lead atom (at mass of lead:207 g mol). 4. Calculate the density of silver which crystallizes in the face centred cubic structure. The distance between the nearest silver atoms in this structure is 287 pm. (molar mass of silver: gmol ). 5. How do ferromagnetism, anti-ferromagnetism and ferromagnetism arise? 6. Give the points of differences between Schottky defect and Frenkel defect? 7. Explain: (i) Why is Frenkel defect not found in pure alkali metal halides? (i) Zinc oxide is white but it turns yellow on heating. (iii) CaClzwill introduce Schottky defect when added to AgCl crystal. '2.7* 8. An element with molar mass 10-2 kg mol forms a cubic unit cell with edge length 405 pm. If the density is2.7*103 kg/m, what is the nature of the cubic unit cell? 9. Explain how can you determine the atomic mass of an unknown metal if you know its mass, density and the dimension of its unit cell? l0.niobium crystallizes in body centered cubic structure. If density is 8.55 g"*t, calculate atomic radius of niobium using its atomic mass (93 u). 1 l. In terms of band theory, what is the difference (i) between a conductor and an insulator (ii) between a conductor and a semiconductor? 12.If the radius of an octahedral void is r and the radius of an atomln close packing is R, derive the relationship between r and R. 13. Calculate the packing efficiency of a face centred cubic crystal.

5 14. How will you distinguish between the following pair of terms? (i) Hexagonal close packing and cubic close packing (ii) Crystal lattice and unit cell (iii) Tetrahedral void and octahedral void. 15. (a) Explain how vacancies are introduced due to an ionic solid when a cation of higher valence is added as an impurity in it? (b) Ionic solids which have anionic vacancies due to metal excess defect develop colour. Explain with the help of a suitable example. (c type of substance ) What or ferromagnetic? Justify your answer. would make better permanent magnets, ferromagnetic 16. Tungsten crystallizes in body centered cubic unit cell. If the edge of the unit cell is pm, what is the radius of atom? tungsten Or Iron has a body centered cubic unit cell with a cell dimension of pm. The density of iron is g/cm. Use this information to calculate Avogadro's nurnber.{at. Mass of Fe: u.) Try Yourself l. An element has a body centered cubic (bcc) structure with a cell edge of 288 pm. The density of the element is7.2 glcm'. How many atoms are present in 208 g of the element? 2. Calculate the packing efficiency of a body centered cubic arrangement. terms: 3. Define the following (i) Space lattice (ii) Femomagnetism (iii) F-centers. 4. Calculate the value of Avogadro's number from the following data: Density of NaCl:2.165 glcm3 Distance between Na* and Cl in NaCl:281 pm. 5. The density of chromium metpl is 7.2 glcm3. If the unit cell is cubic with edge length of 289 pm, determine the type of unit cell (simple body centred or face centred) (Atomic mass of Cr:52 a.m.u, N6:(.Q2x 162:; 6. How will you distinguish between the following pairs of terms? (i) Hexagonal close packing and cubic close packing Crystal lattice and unit cell. (ii) (iii) Tetrahedral void and octahedral voild. 7. Aluminum crystallizes in a cubic close packed structure. (a) What is the lenglh of the side of unit cell. (b) How many unit cells are there in 1.00 cm3 of Al? 8. Explain the following ternis with suitable examples? (a) Schottky defect. Its metallic radius is 125 pm. (b) Frenkel defect (c) Interstitials. 9. X-ray diffraction studies shop that copper uystallizes in an'fcc unit cell with cell edge of 3.608*10-8 copper is determined to have a density of 8.92 cm. In a separate experiment glcm3. Calculate the atomic mass of copper. 1

6 10. What is a semiconductor? Describe the two main types of semiconductor and contrast their condition mechanism. 11. Copper crystallizes with face centred cubic unit cell. If the radius of copper atomis pm, calculate the density of copper metal. (Atomic mass of Cu:63.55 u and Avogadro's number No : 6.02* 1023 mol) 12.Iron has a body centred cubic unit cell with the cell dimension of pm. Density of iron is 7.87 g '. Use this information to calculate Avogadro's number (Atomic mass of " Fe:56.0 u).

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8 5. Give one example each of (i) addition polymers (ii) condensation polymers (iii) Copolymers. 6. Write the structure of the monomer of each of the following polymers: (i) Nylon 6, (ii) Teflon (iii) Neoprene - 7. What is the repeating unit in the condensation polymer obtained by combining HO2CCH2CH2CO2H (succine acid) and HzNCHzCH2NH2 (ethylene dimine)? 8. Differentiate between molecular structure polymers. Give one example of each type. and behaviours of thermoplastic and thermosetting 9. How are polymers classified on the basis of forces operating between their molecules? To which of these classes doe nylon-6,6 belong? 10. Give one example for each of the following: (i) Thermoplastic (ii) Natuilt polymer (iii) Condensation (iv) Chain growth polymer. I L Briefly describe the following terms giving one example of each: (i) Polyolefins (ii) Polyamides (iii) Polyesters I 12. (i) How does vulcanization change the properties of natural rubber? (ii) Why are the numbers 6,6 and 6 put in the names of nylon 6,6 and nylon 6? 13. Write equations for the synthesis of the given polymers (i) Glyptal (ii) Teflon. 14. How does the presence of derivative? benzoquinone inhibit the free radical polymerization of a vinyl 15. Write the information asked in the following polymers: (i) Bakelite-Materials used for preparation (ii) Nylon-6,6-Materials required for preparation, (iii) Synthetic rubber - Monomeric repeating unit (iv) PVC-Monomeric repeating unit. 16. Write the names and the structures of monomers of following polymers: (i) Natural rubber (ii) Terylene 17. Give the preparation and uses of PVC (polyvinyl chloride). 18. What is vulcanization? Why is it done? Why is diphenyl amine added to rubber? 19. Which of the following polymers soften on heating and harden on cooling? What are the polymers with this property collectively called? What are the structural similarities between such polymers? name PMMS? is its use? 20. is the commercial of What What

9 2l.Explain the following processes with the suitable example in each case: (i) Chain growth polymerization (ii) Step growth polymerization 22.How is the following resin intermediate prepared and which polymer is formed by this monomer unit? 23. Why should the monomers very pure? used in addition polymerization through free radical pathway be 24. Can nucleic acids, proteins and starch be considered as step growth polymers? 25.Low density polythene and high density polythene, both are polymers of ethane but there is marked difference in their properties. Explain. 26.Drawthe structure Polypropene of ihe monomer for each of the following polymers: (i) Nylon 6 (ii) 2T.Explain the following terms giving a suitable example for each: (i) Elastomers (ii) Condensation polymers (iii) Addition polymers. { High order thinking skills. 1. Explain why free radical polymerization of styrene gives a product in which phynyl groups are on alternate carbon atoms rather than on adjacent carbon atoms. 2. A monomer of a polymer upon ozonolysis gives one mole of methyglyoxal and two moles or formaldehyde. (i) Identify the monomer of the polymer. (ii) Give its free radical mode of addition polymerization. r