Q69 / 180 · AIIMS 2011 · Chemistry

Assertion : $b c c$ and $h c p$ has same packing efficiency. Reason : Both have same number of atoms per unit cell and same arrangement.

  • A
    If both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
  • C
    If assertion is true but reason is false.
  • Correct answer
    D
    If both assertion and reason are false.

Solution

bcc has $68 \%$ and $h c p$ has $74 \%$ packing efficiency. $b c c$ - 2 atoms per unit cell, $h c p-4$ atoms per unit cell In $b c c$, particles are present at corners and one particle is present at the centre within the body of the unit cell. In hcp, the packing gives a hexagonal pattern.

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

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