Q23 / 77 · NTA Abhyas (JEE Main) 2020 · Chemistry · Solid State

A metallic element crystallizes into a lattice containing a sequence of hexagonal layers of ABABAB....... What percentage by volume of this lattice is empty space?

  • Correct answer
    A
    26%
  • B
    74%
  • C
    50%
  • D
    85%

Solution

Number of atoms in hcp is 6 per unit cell.

Packing fraction = 6× 4 3 πr 3 Base area×C

Base area =6×344r2

C=4r23

Packing fraction =π32=0.74

Void % =1-0.74×100=26%

Hence, the correct answer is option: 'A'.

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