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. |
1. | (A) is false but (R) is true. |
2. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
3. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
4. | (A) is true but (R) is false. |
Which statements among the following is not correct?
1. | When conduction band and valence band overlap, a semiconductor is obtained |
2. | Ferrimagnetism arises due to the alignment of magnetic moments of the domains in the substance in parallel and anti-parallel directions in unequal numbers |
3. | Replacing some silicon atoms by boron atoms in crystal of silicon produces p-type semiconductor |
4. | Replacing some germanium atoms by phosphorus atoms in a crystal of germanium produces n-type semiconductor |
List-I (Defects) |
List-II (shown by) |
(a) Frenkel defect | (i) non-ionic solids and density of the solid decreases. |
(b) Schottky defect | (ii) non-ionic solids and density of the solid increases. |
(c) Vacancy defect | (iii) ionic solids and density of the solid decreases. |
(d) Interstitial defect |
(iv) ionic solids and the density of the solid remains constant. |
(a) | (b) | (c) | (d) | |
1. | (i) | (ii) | (iii) | (iv) |
2. | (i) | (iii) | (ii) | (iv) |
3. | (iv) | (iii) | (ii) | (i) |
4. | (iv) | (iii) | (i) | (ii) |
A compounds that can show both, Frenkel as well as Schottky defects is -
1. AgBr
2. AgI
3. NaCl
4. ZnS
The incorrect statement among the following is -
1. | Density decreases in case of crystals with Schottky's defect. |
2. | NaCl(s) is insulator, silicon is semiconductor, silver is conductor, quartz is piezo electric crystal. |
3. | Frenkel defect is favoured in those ionic compounds in which sizes of cations and anions have large difference. |
4. | \(Fe_{0.98}O\) has non stoichiometric metal excess defect. |
The correct statement regarding defects in a crystalline solid is:
1. | Schottky defects have no effect on the density of crystalline solids. |
2. | Frenkel defects decrease the density of crystalline solids. |
3. | Frenkel defect is a dislocation defect. |
4. | Frenkel defect is found in halides of alkaline metals. |
Silicon gives p-type of semiconductor on doping with:
1. Germanium.
2. Arsenic.
3. Selenium.
4. Boron.
The appearance of colour in solid alkali metal halides is generally due to:
1. F-centres.
2. Schottky defect.
3. Frenkel defect.
4. Interstitial positions.
Schottky defect shows:
1. | Same number of cation and anions decrease from lattice. |
2. | Cations and anions are replaced from their sites. |
3. | Maximum number of cations and anions are same. |
4. | None of the above. |