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The Solid State
Imperfections in Solids – Point Defects
2 questions from 2 papers, each with its answer.
- questions
- 2
- papers
- 2
- years asked, 2017–2026
- 2 of 10
- of The Solid State
- 4.44%
Appears in
Concepts tested
- Frenkel defect and electrical neutrality
- solid-state-defects
All Questions
2022 1 question
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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.Assertion is correct: in point defects of ionic solids, electrical neutrality is maintained (the given case is an example of metal deficiency defect). Reason is correct: in Frenkel defect, a cation is dislocated from its lattice site to an interstitial site, maintaining electrical neutrality. But in Frenkel defect no cation is missing from the crystal, so the Reason is not the correct explanation of the Assertion. So both A and R are correct but R is not the correct explanation of A.
2017 1 question
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Which is the incorrect statement?
Frenkel defects need a large size difference between ions.
Frenkel defect occurs in those ionic compounds in which the sizes of cation and anion are largely different, so the statement about Frenkel defect is incorrect. Non-stoichiometric ferrous oxide is $Fe_{0.93-0.96}O_{1.00}$ and it is due to metal deficiency defect, so the formula $FeO_{0.98}$ in the statement is also incorrect. Note: the source key accepts both the $FeO_{0.98}$ statement and the Frenkel-defect statement as incorrect statements.