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NEET-XII-Chemistry

01: The Solid State

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  • #18
    An element with molar mass 2.7 × 10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 × 103 kg m-3, what is the nature of the cubic unit cell?
    Ans : It is given that density of the element, d = 2.7 × 103 kg m-3

    Molar mass, M = 2.7 × 10-2 kg mol-1

    Edge length, a = 405 pm = 405 × 10-12 m

    = 4.05 × 10-10 m

    It is known that, Avogadro’s number, NA = 6.022 × 1023 mol-1

    Applying the relation,



    This implies that four atoms of the element are present per unit cell. Hence, the unit cell is face-centred cubic (fcc) or cubic close-packed (ccp).