The Solid State

  • Question 85
    CBSEENCH12005433

    What is the difference between ccp and fcc lattice?

    Solution
    These are two different names for the same lattice.
    so there is no difference between ccp and fcc.
    Question 86
    CBSEENCH12005434

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

    Solution
    (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
    CBSEENCH12005435

    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?

    Solution
    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
    CBSEENCH12005436

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

    Solution
    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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