Q59 / 180 · AIIMS 2013 · Chemistry

Assertion: The presence of a large number of Schottky defects in $\mathrm{NaCl}$ lowers its density. Reason : In $\mathrm{NaCl}$, there are approximately $10^6$ Schottky pairs per $\mathrm{cm}^3$ at room temperature.

  • A
    If both assertion and reason are true and reason is the correct explanation of assertion.
  • Correct answer
    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.
  • D
    If both assertion and reason are false.

Solution

When an atom or an ion is missing from its normal lattice site, a lattice vacancy or defect is created, which is called Schottky defect. Due to missing density of crystal will be lowered.

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

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