Question

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

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

Options

• If both Assertion and Reason are CORRECT and Reason is the CORRECT explanation of the Assertion.

• If both Assertion and Reason are CORRECT but Reason is not the CORRECT explanation of the Assertion.

• If Assertion is CORRECT but Reason is INCORRECT.

• If Assertion is INCORRECT but Reason is CORRECT.

Answer 1

If both Assertion and Reason are CORRECT but Reason is not the CORRECT explanation of the Assertion.

Explanation:

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 anions are also absent.

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.