The Solid State

  • Question 113
    CBSEENCH12005461

    How will you distinguish between the following pairs of terms:
    Crystal lattice and unit cell?

    Solution
    Question 114
    CBSEENCH12005462

    How will you distinguish between the following pairs of terms:
    Tetrahedral void and octahedral void?

    Solution
    Question 115
    CBSEENCH12005463

    How many lattice points are there in one unit cell of each of the following lattice?
    (i) face centered cubic
    (ii) face centered tetragonal
    (iii) body centered.

    Solution

    Solution:

    (i) One unit cell of a face-centered cubic has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

    (ii) One unit cell of face-centered tetragonal has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

    (iii) One unit cell of body centered has 8 lattice points are corners and 1 lattice points at faces, total 9 lattice points.

    Question 116
    CBSEENCH12005464

    Explain the basis of similarities and differences between metallic and ionic crystals.

    Solution
    The similarities and differences between metallic and ionic crystals are described as below:

    Characteristics

    Ionic crystals

    Metallic crystals

    1.

    Constituent particles

    cations (positive ions) and anions (negative ions)

    Positive ions and mobile electrons.

    2.

    Binding forces

    Strong electrostatic forces (electro valent bonding)

    Electrical attraction between positive ions and mobile electrons (metallic bonding)

    3.

    Physical properties

    Hard and brittle; high m.p. and b.p. good conductors of heat and electricity in molten state and aqueous solution, high heat of fusion.

    Hard but malleable, high m.p., very good conductors of heat and electricity in solid and molten state, moderate heats of fusion.

     

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