5. Assertion : The presence of a large number of Schottky defects in NaCl lowers its density. Reason : In NaCl there are approximately

10⁶ Schottky pairs per cm³ at room temperature.

a. If both assertion and reason are true and the reason is the correct explanation of the assertion

b. If both assertion and reason are true but reason is not the correct explanation of the assertion

c. If assertion is true but reason is false

d. If the assertion and reason both are false

e. if assertion is false but reason is true.

Ans. b

Explanation : 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.