# 1. Iron(II) oxide crystallize as Fe 0.93O. Find the %Fe2+ and Fe3+ in this compound 2. A Solid AB has NaCl structure. If the radius of cation A+ is 100 pm, what is the possible maximum and minimum radius of anion B- 3. If the radius of Mg2+, Cs+, O2-,S2- and Cl- ion are 0.65 A0, 1.69 A0, 1.40 A0, 1.84 A0 and 1.81 A0 respectively. Find the coordination number of MgO,MgS and CsCl. 4. In corundum, oxide ion are in hcp and aluminium ion occupy 2/3 of the octahedral void. What is the formula of aluminium oxide? 5. A cubic solid is made up of two elements P and Q. Q occupies corners of the cube and P occupies the body centre. What is the formula of the compound? 6. In a crystalline solid anion C occupies ccp, cation A occupies 50% tetrahedral void and cation B occupies 50% octahedral void. What is the formula of the compound? 7. If NaCl is doped with 10-3 mole % SrCl2 . What is the concentration of cation vacancies? 8. Sodium metal crystallizes in bcc with a cell edge of 4.3 A0. What is the radius of sodium atom? 9. Copper crystallizes in fcc with a density 9g/cm3.Calculate the radius of copper atom (Atomic mass of Cu=63) 10. Cr crystallizes in bcc with atomic diameter 250pm. Determine the density of unit cell. (Atomic mass of Cr=52) 11. Calculate the value of Avagadro number. Given Density of unit cell of NaCl=2.165 g/cm3 Distance between Na+ and Cl- is 281pm. Atomic mass of NaCl= 58.5. 12. CsBr has bcc structure.a= 400pm Calculate the distance between Cs+ and Br- 13. KF has NaCl structure. Find the distance between K+ and F-. Density of unit cell= 2.5 g/ cm3 ( Molar mass of KF = 58 ) 14. An element crystallizes in bcc. a = 288 pm. How many atoms are there in 208 grams of this elements? 15. An element crystallizes in fcc with a = 200 pm. Calulate its density if 200grams of this element contains 24x 1023 atoms. 16. Unit cell of an element has atomic mass 108. d= 10.5 g/cm3 a= 409 pm. Find the structure of the crystal lattice. 17. A compound has hexagonal close packing structure. Determine the total number of voids, number of tetrahedral void, and number of octahedral voids in 0.5 mole of this compounds. 18. Al crystallizes in a cubic close packing structure. Its metallic radius is 125 pm .Find the edge length of the unit cell. How many unit cells are there in 1cm3 of Al ? How many atoms are there in 1cm3 of Al ? 19. Silver chrysalises in FCC with an edge length 409 pm and density 10.5g/cm3. Calculate the Atomic mass of silver.

### Asked by Shubham Goyal | 9th Mar, 2013, 07:04: AM

Expert Answer:

### ans 1. Fe o.93 O 1.O means 93 Fe ions have combined with O 2- Ions.
suppose Fe present as Fe 3+ is x, then Fe 2 + would be 93 - x .
for the compound to be neutral, the sum charge on the compound ought to be o. thus,
3 x + 2 ( 93 - x ) = 2 x 100 O
OR 3x + 18 - 2x = 200. or x = 14.
or Fe 3 + = 14.
So, Fe 3 + will be 93 - 14 = 79.
now the formula becomes Fe 2+ 0.79 Fe 3 + 0.14 O 2- 1.0
total molar mass = 0.92 x 56 + 1 x 16 = 68.08 g .
Fe 3 + = 0.14 x 56 = 7.84g
% Fe 3 + present = 7.84 x 100.
68.08
= 11.5 %

### Answered by | 10th Mar, 2013, 10:16: PM

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