Question

Assertion (A): In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.
Reason(R): In an ionic solid, Frenkel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality.
Choose the most appropriate answer from the options given below:

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct and (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Answer 1

The Correct Option is B

To determine the most appropriate answer, we need to analyze both the assertion and the reason given.

Assertion (A): In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.

Explanation of (A): If cations are missing, such a point defect is known as a Schottky defect. In a Schottky defect, equal numbers of cations and anions are missing, preserving the overall electrical neutrality of the ionic solid. Therefore, the assertion is correct because the absence of some cations does not disturb the electrical neutrality as enough number of anions are also absent.

Reason (R): In an ionic solid, Frenkel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality.

Explanation of (R): A Frenkel defect involves a cation moving from its regular lattice position to an interstitial site, leading to a dislocation and not a loss of cations from the crystal structure. Thus, electrical neutrality is maintained in Frenkel defects as no ions are actually lost from the crystal. Therefore, the reason is also correct.

However, the given reason does not directly explain the assertion correctly. The assertion mentions the absence of cations which correlates with Schottky defect, not Frenkel defect.

Thus, the proper conclusion is:

Both (A) and (R) are correct and (R) is not the correct explanation of (A)