Incorrect statement among the following about amorphous solids is -
1. | On heating they may become crystalline at a certain temperature. |
2. | They may become crystalline on keeping for a long time. |
3. | Amorphous solids can be moulded by heating. |
4. | They are anisotropic in nature. |
Iodine molecules are held in the crystals lattice by ........ .
1. London forces.
2. Dipole-dipole interactions.
3. Covalent bonds.
4. Coulombic forces.
Network solid, among the following, is :
1. SO2(solid)
2. I2
3. Diamond
4. H2O(ice)
I. Mg(s)
II. TiO(s)
III. I2(s)
IV. H2O(s)
The insulator among the given examples is -
1. Only I
2. Only II
3. III and IV
4. II, III, and IV
Graphite is a good conductor of electricity due to the presence of ......... .
(1) Lone pair of electrons.
(2) Free valence electrons.
(3) Cations.
(4) Anions.
Graphite cannot be classified as ...........
1. Conducting solid.
2. Network solid.
3. Covalent solid.
4. Ionic solid.
Cations are present in the interstitial sites in ............ .
1. Frenkel defect.
2. Schottky defect.
3. Vacancy defect.
4. Metal deficiency defect.
Schottky defect is observed in crystals when:
1. | Some cations move from their lattice site to interstitial sites. |
2. | Equal number of cations and anions are missing from the lattice. |
3. | Some lattice sites are occupied by electrons. |
4. | Some impurities are present in the lattice. |
Chargewise p-type semiconductor is -
1. Positive.
2. Neutral.
3. Negative.
4. Depends on the concentration of p impurity.
To get a n-type semiconductor from silicon, it should be doped with a substance with valency -
1. 2
2. 1
3. 3
4. 5