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
If Z is the number of atoms in the unit cell that represents the closest packing sequence... A B C A B C..., the number of tetrahedral voids in the unit cell is equal to
Z
2Z
Z/2
Z/4
Assertion : Graphite is an example of tetragonal crystal system.
Reason : For a tetragonal system, a = b c, == 90°,= 120°
If both assertion and reason are true but reason is not the correct explanation of the assertion.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
If assertion is true, but reason is false.
Both assertion and reason are false statements.
An element (atomic mass 100 g/mol) having BCC structure has unit cell edge 400 pm. The density of element is (No. of atom in BCC (Z) = 2).
2.144 g/cm3
7.289 g/cm3
5.188 g/cm3
10.376 g/cm3
The crystal system of a compound with unit cell dimensions a= 0.387 nm, b= 0.387 nm and c = 0.504 nm and 90° and 120° is
Cubic
Hexagonal
Orthorhombic
Rhombohedral
A solid AB has NaCl type structure. The radius of A+is 100 pm. What is the radius of B-?
190.47
540.13
525
78.12