A metal has a fcc lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm$$-$$3. The molar mass of the metal is
(NA Avogadro's constant = 6.02 $$ \times $$ 1023 mol$$-$$1)
Structure of a mixed oxide is cubic close packed (ccp). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are cooupied by a monovalent metal B. The formula of the oxide is
A
ABO2
B
A2BO2
C
A2B3O4
D
AB2O2
Explanation
Number of atoms in cubic close packing = 4 = O2-
Number of tetrahedral voids = 2 × N = 2 × 4
Number of A2+ ions = 8 $$ \times $$ $${1 \over 4}$$ = 2
Number of octahedral voids
= Number of B+ ions = N = 4
Ratio of ions will be,
O2– : A2+ : B+ = 4 : 2 : 4 = 2 : 1 : 2
Formula of oxide = AB2O2
3
AIPMT 2012 Prelims
MCQ (Single Correct Answer)
The number of octahedral void(s) per atom present in a cubic close-packed structure is
A
1
B
3
C
2
D
4
Explanation
Number of octahedral voids is same as number
of atoms.
4
AIPMT 2012 Prelims
MCQ (Single Correct Answer)
A metal crystallises with a face-centred cubic lattice. The edge of the unit cell is 408 pm. The diameter of the metal atom is