1. | \( 1 \over 12\) | 2. | \( 1 \over 2\) |
3. | \( 1 \over 3\) | 4. | \( 1 \over 4\) |
1. | \(1.550 \times10^{24}\) | 2. | \(3.011 \times10^{25}\) |
3. | \(3.011 \times10^{24}\) | 4. | \(6.022 \times10^{24}\) |
1. | \(a = 2r\) | 2. | \(a = r /2\sqrt2\) |
3. | \(a = 4r /\sqrt3\) | 4. | \(a = 2\sqrt2r\) |
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. |
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because:
1. | all the domains get oriented in the direction opposite to the direction of magnetic field. |
2. | domains are not affected by magnetic field. |
3. | domains get randomly oriented. |
4. | all the domains get oriented in the direction of magnetic field. |
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) |
The number of tetrahedral and octahedral voids in hexagonal primitive unit cell are respectively:
1. 2, 1
2. 12, 6
3. 8, 4
4. 6, 12