What makes the crystal of KCl appear sometimes violet?
This is due to F centre, electron become exicted and when they come to ground state they radiate energy in visible reigon.
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Multiple Choice Questions
If the distance between Na+ and CI– ions in NaCl crystal is a pm, what is the length of the cell edge?
2a pm
a / 2 pm
4a pm
a/4 pm
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The presence of F-centres in a solid makes it
conducting
colourless
coloured
non-conducting
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Short Answer Type
What is the effect of Schottky and Frenkel defects on the density of crystalline solids?
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Multiple Choice Questions
The available space occupied by spheres of equal size in three dimensions in both hcp and ccp arrangements is:
74%
70%
60.4%
52.4%
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Most crystals show good cleavage because their atoms, ions and molecules are
Weakly bonded together
strongly bonded together
spherically symmetrical
arranged in planes.
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CsCl has which type of lattice?
SC
fcc
bcc
hcp
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The tetrahedral voids formed by ccp arrangement of CI– ions in rock salt structure are:
Occupied by Na+ ions
Occupied by CI– ions
Occupied by either Na+ or CI– ions
Vacant
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A compound is formed by elements A and B. This crystallises in the cubic structure when atoms A are at the corners of the cube and atoms B are at the centre of the body. The simplest formula of the compound is:
AB
AB2
A2B
AB4
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Short Answer Type
Name the crystal defect which lowers the density of an ionic crystal