Assainment:2 CHEM –XII
SOLID STATE
1. What is the formula of a compound which the element Y forms ccp lattices and atoms of X occupy
2/3rd of octahedral voids? [1]
2. An element X (molecular mass 60g cm-1) has a density of 6.23 g cm-3. Identify the type of cubic unit
cell, if the edge length of the unit cell is 4 x 10 -8cm. [3]
3. Express the relationship between atomic radius (r) and edge length (a) in a unit cell. [1]
4. a. What type of stoichiometric defect is shown by KCl and Why?
b. What type of semiconductor is formed when Si is doped with As?
c. Which one of the following is an example of molecular solid: CO2 or SiO2?
d. What type of substance would make better magnets ferromagnetic or ferromagnetic? [3]
5. Which group of solids are electrical conductors, as well as malleable and ductile? [1]
6. Why glass is considered a super cooled liquid? [1]
7. What is the two dimensional co-ordination number of a molecule in a square close-packed layer? [1]
8. An element with molecular mass 27 gmol-1 forms a cubic unit cell with edge length 4.05 x 10 -8 cm. If
its density is 2.7 g cm-1, what is the nature of the unit cell? [3]
9. What is meant by forbidden zone in reference to band theory of solid? [1]
10. What is meant by doping in a semiconductor? [1]
11. Write a point of distinction between a metallic solid and an ionic solid other than metallic luster. [1]
12. How may the conductivity of an intrinsic semiconductor be increased? [1]
13. Which stoichiometric defect increases the density of the solid? [1]
14. What are n-type semiconductors? [1]
15. Tungsten crystallizes in bcc. If the cell edge is 316.5pm. What is the radius of tungsten atom? [3]
16. Iron has a bcc with cell dimensions of 286.65pm. the density of iron is7.874 gcm -3. Use this find
Avogadro number.(At. Mass of Fe is 55.845 amu) [3]
17. Copper crystallizes with fcc. If the radius of Cu atom is 127.8pm, calculate the density of Cu. [ At
Mass of Cu = 63.55 u, NA = 6.02 x 10 23 mol-1.] [3]
18. Define paramagnetsism with an example. [1]
19. Crystalline solids are “anisotropic in nature”. What does this statement mean? [1]
20. Explain how you can determine the atomic mass of an unknown metal if you know its mass, density
and the dimensions of unit cell of its crystal. [2]
21. Define the following terms in relation to crystalline solids.
a. Uunit cell
b. co-ordination number. Give examples in each case. [2]
22. What is meant by an intrinsic semiconductor? [1]
23. How many atoms are there in one unit cell of a bcc crystal? [1]
24. Silver crystallizes in fcc. Edge length is 400 pm. Calculate radius of Ag atom. [3]
25. The density of lead is 11.35 g cm-3 and the metal crystallizes with fcc unit cell. Estimate the radius of
lead atom. [At Mass of lead =207 g mol-1, NA = 6.02 x 10 23 mol-1] [3]
26. Calculate the packing efficiency of a metal crystal for a simple cubic lattice. [2]
27. Aluminium crystallizes in a cubic close packed structure. Radius of the atom in the metal is 125pm.
a. What is the edge length of the side of unit cell?
b. How many unit cells are there in 1cm3 of Aluminium? [3]
28. Write a feature which will distinguish a metallic solid from an ionic solid. [1]
29. The well-known mineral fluorite is chemically calcium fluoride. It is known that in one unit cell of
this mineral there are 4 Ca2+ ions and 8 F- ions and that ca2+ ions are arranged in fcc lattice. The Fions fill all the tetrahedral holes in the fcc lattice of Ca2+ ions. The edge of the unit cell 5.46 x10 -8 cm
in length. The density of solid is 3.18 g cm-3. Calculate Avogadro number.
[Molecular mass of CaF2 is 70.08g mol-1] [3]
30. Which point defect in crystals of a solid does not change the density of a solid? [1]
31. What type of interactions hold the molecules together in a polar molecular solid? [1]