NaCl sometimes appear yellow in colour because of :
Reaction with air.
Metal excess defect due to anionic vacancies.
Metal deficiency defect due to cation vacancies.
Schottky defect.
FeO(s) is not formed in stoichiometric composition because :
Three Fe2+ ions are replaced by two Fe3+ ions.
Two Fe2+ ions are replaced by three Fe3+ ions.
Three Fe2+ ions are replaced by three Fe3+ ions.
Two Fe2+ ions are replaced by two Fe3+ ions.
White ZnO (s) becomes yellow upon heating due to shifting of :
Protons to interstitial sites and F-centres.
Electrons to interstitial sites and F-centres.
Photons to interstitial sites and F-centres.
Neutrons to interstitial sites and F-centres.
The electrical conductivity of semiconductors increase with rise in temperature because -
Electrons jump from the valence band to the conduction band.
Electrons jump from the conduction band to the valence band.
No electrons jump from the valence band to the conduction band.
No electrons jump from the conduction band to the valence band.
The conductivity of germanium crystals increases on doping with galium because :
Occupation of lattice site of germanium by galium.
Occupation of lattice site of galium by germanium.
Of presence of extra electron in the lattice.
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 :
M2N3
M3N2
MN
M2N4
Amorphous substance changes to crystalline form :
On heating.
On pressure.
In light.
In UV source.
Mg in solid-state shows electronic conductivity due to the presence of-
Positive holes.
No electrons.
None of the above
MgCl2 in the molten state is-
p-type semiconductor
n-type semiconductor
Electrolytic conductors
Electronic conductors
Cubic close packing in three dimensions is
Triangular voids
Pattern of spheres is repeated in every fourth layer
Coordination number =4
Pattern of sphere is repeated in alternate layers
Number of octahedral voids are present per unit cell in a cubic close packed structure :
4
8
6
2
Number of tetrahedral voids voids are present per unit cell in a cubic close packed structure :
Doping affects the property of semiconductors. It -
Increases the conductivity of semiconductors.
Decreases the conductivity of semiconductors.
No effect on conductivity of semiconductors.
Non-stoichiometric defect present in the sample of ferrous oxide with formula Fe0.93O1.00 -
Metal deficiency defect
Metal excess defect
Frenkel defect
Schottky defect
Assertion: The stability of a crystal is reflected by the magnitude of its melting point.
Reason: Greater the intermolecular forces of attraction, the more will be the stability and melting point of the substance.
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
The packing efficiency of the face-centered cubic unit cell (with the assumptions that atoms are touching each other) is-
52.40 %
68.04 %
74 %
79.06 %
Silver crystallizes in fcc lattice. If the edge length of the cell is 4.07 × 10−8 cm and density is 10.5 g cm−3. The atomic mass of silver is -
120.31 g mol-1
107.9 g mol-1
207.60 g mol-1
138.52 g mol-1
Copper crystallizes into a fcc lattice with an edge length of 3.61 × 10−8 cm. The density of copper crystal will be -
7.46 g cm-3
9.67 g cm-3
8.96 g cm-3
5.63 g cm-3
Nickel oxide has the formula Ni0.98O1.00. The fraction of nickel existing as Ni3+ ions will be -
0.041
0.959
0.736
0.264
A ferric oxide crystallizes in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. The formula of the ferric oxide is-
Fe3O4
FeO
Fe2O3
Fe3O2
The second order Bragg diffraction of X-rays with λ = 1.00 Å from a set of parallel planes in a metal occurs at an angle 60°. The distance between the scattering planes in the crystal is :
A compound forms a hexagonal close-packed structure. The total number of voids in 0.5 moles
of the compound will be -
1. 9.033 × 10232. 3.011 × 10233. 6.023 × 10234. 8.024 × 1023
A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. The formula of the compound would be -
M3N4
An element with a molar mass of 2.7 × 10-2 kg mol-1 and density 2.7 × 103 kg m-3 forms
a unit cell with an edge length of 405 pm. The type of unit cell is-
Simple cubic cell.
Face centered cubic cell.
Body-centered cubic cell.
Solid A is a very hard electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?
H-bonded molecular solid
Ionic solid
Covalent or network solid
Metallic solid
The incorrect statement among the following regarding crystalline solid is -
Definite and characteristic heat of fusion.
Isotropic nature.
A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal.
A true solid.
An example of amorphous solid among the following is -
Graphite (C)
Quartz glass ( SiO2 )
Chrome alum
Silicon carbide (SiC)
Which of the following arrangements shows the schematic alignment of magnetic moments of antiferromagnetic substances?
↑ ↑ ↑ ↑ ↑ ↑
↓ ↓ ↓ ↓ ↓ ↓
↑ ↑ ↓ ↑ ↑ ↓
↑ ↓ ↑ ↓ ↑ ↓
Incorrect statement among the following about amorphous solids is -
On heating they may become crystalline at a certain temperature.
They may become crystalline on keeping for a long time.
Amorphous solids can be moulded by heating.
They are anisotropic in nature.
Iodine molecules are held in the crystals lattice by ........ .
London forces.
Dipole-dipole interactions.
Covalent bonds.
Coulombic forces.
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