Q-1. How many spheres are in contact with each other in a single plane of a close packed structure?
Ans-1. Six(6).
Q-2. Name the two closest packed arrangements of identical spheres.
Ans-2. a) Hexagonal close- packed arrangement
b) Cubic closest packed arrangement.
Q-3. What is the coordination number of a sphere in a
a) Hexagonal close –packed structure
b) Cubic close packed structure
c) body –centered cubic close -packed structure
d) face – centered cubic close- packed structure.
Ans-3. a) 12 b)12 c) 8 d)12
Q-4. W hat is the non- stoichiometry defect in the crystals ?
Ans-4.These defects occur when the ratio of the cations and anions in the resulting compound is different from that as indicated by the laws of the chemical combinations.
Q-5. How many atoms are there in a
a) simple or primitive unit cell
b) body centered cubic unit cell
c) face centered cubic unit cell
Ans-5. a) one b) two c) four.
Q-6.W hat other elements may be added to silicon to make electrons available for the conduction of an electric current?
Ans-6. Phosphorous or Gallium.
Q-7. How many octahedral sites per sphere are there in a cubic closest – packed ( face centered cubic) structure.?
Ans-7. One.
Q-8. How many Tetrahedral sites per sphere are there in a cubic closest – packed ( face centered cubic) structure.?
Ans-8. Two.
Q-9. I f the formula of an ionic compound is AB, can the cation A occupy all the a) tetrahedral voids
b) octahedral voids
Ans-9. a)No, the cation A can occupy only ½ of the tetrahedral voids.
b) Yes , the cation A can occupy all the octahedral voids.
Q-10. What is the coordination no. of an octahedral void ?
Ans-10. Six(6).
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