Solid State - Result Question 19
####19. A compound $M _p X _q$ has cubic close packing (ccp) arrangement of $X$. Its unit cell structure is shown below. The empirical formula of the compound, is
(2012)
(a) $M X$
(b) $M X _2$
(c) $M _2 X$
(d) $M _5 X _{14}$
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Answer:
Correct Answer: 19. (b)
Solution:
- Contribution of atom from the edge centre is $1 / 4$. Therefore, number of
$M=\frac{1}{4} \times 4$ (from edge centre) +1 (from body centre) $=2$
Number of $X=\frac{1}{8} \times 8$ (from corners) $+\frac{1}{2} \times 6$
$\Rightarrow$ Empirical formula $=M _2 X _4=M X _2$
$($ from face centre $)=4$
