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, polyvinyl chloride, fibreglass, copper
1.4.Why is glass considered a supercooled 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 of intermolecular 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 state and 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
1.13. Explain how much portion of an atom located at
1.14. What is the two-dimensional coordination number of a molecule in square close-packed layer?
1.15. 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?
1.16. A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy l/3rd of tetrahedral voids. What is the formula of the compound?
1.17. Wh ich of the following lattices has the highest packing efficiency (i) simple cubic (ii) body- centred cubic and (iii) hexagonal close-packed lattice?
1.18. An element with molar mass 2.7 x 10-2 kg 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?
1.19. What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?
1.20.What type of stoichiometric defect is shown by:
1.21. Explain how vacancies are introduced in an ionic solid when a cation of 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 doping it 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.
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 what conditions could quartz be converted into glass?
1.3 Classify each of the following solids as ionic, metallic, modular, network (covalent) or amorphous:
1.4 (i) What is meant by the term ‘coordination number’?
1.5 How can you determine the atomic mass of an unknown metal if you know its density and the dimensions 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 ether and methane from a data book. What can you say about the intermolecular forces between these molecules?
1.7 How will you distinguish between the following pairs of terms:
1.8 How many lattice points are there is one unit cell of each of the following lattices?
1.10 Calculate the efficiency of packing in case of a metal crystal for (i) simple cubic, (ii) body centred cubic, and (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 x 10-8 cm and density is 10.5 g cm-3, calculate the atomic mass of silver.
1.12 A cubic solid is made up 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?
1.13 Niobium crystallises in a body centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium, using its atomic mass 93u.
1.14 If the radius of the octahedral void is r and radius of the atoms in close-packing is R, derive relation between rand R.
1.15 Copper crystallises into a fee lattice with edge length 3.61 x 10-8 cm. Show that the calculated density is in agreement with its measured value of 8.92 gcm-3.
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