NEET Chemistry The Solid State Questions Solved

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Copper crystallises with face centred cubic unit cell. If the radius of copper atom is 127.8 pm, calculate the density of copper metal.

(Atomic mass of Cu = 63.55 u and Avogadro's number NA = 6.02 ×1023 mol-1)

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Concept Questions :-

Density/Formula/packing fraction/ Semiconductors

In fcc, lattice, Z = 4 atoms  [fcc = face centred cubic]

Formula : d = Z×Ma3×NA

fcc lattice for copper a = 22r

a3 = (22r)3

 a3 = 8×22(1.278×10-8 cm)3

 a3 = 4.723×10-23 cm3

 

d = 4×63.55 g mol-14.723×10-23cm3××6.02×1023 mol-1

 d = 254.2 g mol-128.43 = 8.94 g cm-3

 

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