In tetragonal crystal system, which of following is not true?
All axial lengths and all axial angles are equal.
All three axial lengths are equal.
All three axial angles are equal.
Two axial angles are equal but the third is different.
In solid ice, oxygen atom is surrounded
tetrahedrally by 4 hydrogen atoms
octahedrally by 2 oxygen and 4 hydrogen atoms
tetrahedrally by 2 hydrogen and 2 oxygen atoms
octahedrally by 6 hydrogen atoms
Schottky defect is
vacancy of ions
delocalization of ions
interstitial vacancy of ions
vacancy of only cations
Assertion : bcc and hcp has same packing efficiency.
Reason : Both have same number of atoms per unit cell and same arrangement.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Assertion: Due to Frenkel defect, density of the crystalline solid decreases.
Reason : In Frenkel defect, cation or anion leaves the crystal.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Schottky defect in crystals is observed when
unequal number cations and anions are missing from the lattice
equal number of cations and anions are missing from the lattice
an ion leaves its normal site and occupies an interstitial site
density of the crystal is increased.
The incorrect statement among the following is
C60 is an allotropic form of carbon
O3, is an allotropic form of oxygen
S8 is only allotropic form of sulphur
red phosphorus is more stable in air than white phosphorus.
C.
S8 is only allotropic form of sulphur
The different allotropic forms ofsulphur arises partly from the extent to which S has polymerised and partly from the crystal structures adopted. The two common crystalline forms are or rhombic sulphur and or monoclinic sulphur. A third modification is -monoclinic sulphur. All three forms contain puckered S8 rings with a crown conformation.
Engel's sulphur (-sulphur) contains S6 rings. S7, S9, S10, S11,S12, S18 and S20 rings have been made by Schmidt and his group. Plastic or -sulphur contains spiral chains and sometimes S8 and other rings. The other allotropic forms of sulphur are milk of
sulphur and colloidal or -sulphur.
The Ca2+ and F- are located in CaF2 crystal, respectively at face centred cubic lattice points and in
tetrahedral voids
half of tetrahedral voids
octahedral voids
half of octahedral voids