NaCl sometimes appear yellow in colour because of :
1. Reaction with air.
2. Metal excess defect due to anionic vacancies.
3. Metal deficiency defect due to cation vacancies.
4. Schottky defect.
FeO(s) is not formed in stoichiometric composition because :
1. Three Fe2+ ions are replaced by two Fe3+ ions.
2. Two Fe2+ ions are replaced by three Fe3+ ions.
3. Three Fe2+ ions are replaced by three Fe3+ ions.
4. Two Fe2+ ions are replaced by two Fe3+ ions.
White ZnO (s) becomes yellow upon heating due to shifting of :
1. Protons to interstitial sites and F-centres.
2. Electrons to interstitial sites and F-centres.
3. Photons to interstitial sites and F-centres.
4. Neutrons to interstitial sites and F-centres.
The electrical conductivity of semiconductors increases with a rise in temperature because:
1. | Electrons jump from the valence band to the conduction band. |
2. | Electrons jump from the conduction band to the valence band. |
3. | No electrons jump from the valence band to the conduction band. |
4. | No electrons jump from the conduction band to the valence band. |
The conductivity of germanium crystals increases on doping with galium because :
1. Occupation of lattice site of germanium by galium.
2. Occupation of lattice site of galium by germanium.
3. Of presence of extra electron in the lattice.
4. None of the above.
In a compound, nitrogen atoms (N) make cubic close packed lattic and metal atoms (M) occupy one-third of the tetrahedral voids present. The formula of the compound formed by M and N is :
1. M2N3
2. M3N2
3. MN
4. M2N4
Amorphous substance changes to crystalline form :
1. On heating.
2. On pressure.
3. In light.
4. In UV source.
Mg in solid-state shows electronic conductivity due to the presence of-
1. Free electrons.
2. Positive holes.
3. No electrons.
4. None of the above
MgCl2 in the molten state is-
1. p-type semiconductor
2. n-type semiconductor
3. Electrolytic conductors
4. Electronic conductors
Cubic close packing in three dimensions is
1. Triangular voids
2. Pattern of spheres is repeated in every fourth layer
3. Coordination number =4
4. Pattern of sphere is repeated in alternate layers