The Solid State - Result Question 16
####16. Structure of a mixed oxide is cubic close-packed (c.c.p). 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 occupied by a monovalent metal $B$. The formula of the oxide is :
[2012 M]
(a) $A B O_2$
(c) $A_2 B_3 O_4$
(b) $A_2 B O_2$
(d) $A B_2 O_2$
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Solution:
- (d) No. of $A^{2+}$ ions $=\frac{1}{4} \times 8=2$
No. of $B^{+}$ions $=4 \times 1=4$
No. of atoms in $c c p$,
$O^{2-}=8 \times \frac{1}{8}+6 \times \frac{1}{2}=4$
Hence the formula of the oxide will be
$A_2 B_4 O_4$ or $A B_2 O_2$.
