Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below :
- Both (A) and (R) are correct and (R) is the correct explanation of (A)
- Both (A) and (R) are correct but (R) is not the correct explanation of (A)
- (A) is correct but (R) is not correct
- (A) is not correct but (R) is correct
Answer
(2) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Solution
Assertion: As per NCERT, in Schottky defect an equal number of cations and anions are missing from the lattice, so the ionic solid remains electrically neutral even though some of its cations are missing. Correct.
Reason: As per NCERT, in Frenkel (dislocation) defect the smaller ion (usually the cation) is dislocated from its normal site to an interstitial site; no ion is lost, so the solid stays electrically neutral. Correct.
The neutrality described in (A), with cations missing from the unit cells, is due to the Schottky defect (equal number of anions also missing), not the Frenkel defect.
(R) is not the correct explanation of (A).
Answer: (2)