The Solid State

Question 85

What is the difference between ccp and fcc lattice?

These are two different names for the same lattice.
so there is no difference between ccp and fcc.
Question 86

What percent of space is utilised by spheres in (i) simple cubic, (ii) face-centered cubic, (iii) body-centered cubic structure?

(i)Packing efficiency in simple cubic lattice = 52.4%,
(ii)packing efficiency in face-centred  cubic lattice =  74%,
(iii) packing efficiency in body centred cubic lattice =  68%.
Question 87

If three elements A, B and C crystallize in a cubic solid lattic with A atom at the corner, B atoms at cube centre and C atoms at edges then what would be the formula of the solid?

Atom A is shared by 8 corners 1
atoms of C is shared by 4 unit cells
Atom B is present at centre of the unit cell
Hence, effective number of atoms of A per unit cell = 8× 1/8 = 1
Effective number of atoms of C per unit cell = 12/4 = 3
Effective number of atoms of B per unit cell = 1 Hence, the formula of the compound is ABC3
Question 88

Out of Schottky and Frenkel defect which increases the dielectric constant of crystals?

Frenkel defect tends to increase the dielectric constant of the crystalt. It is because of the presence of the ions in interstitial sites.

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