Solid State - Result Question 43
43. A metal crystallises into two cubic phases, face centred cubic (fcc) and body centred cubic (bcc), whose unit cell lengths are $3.5$ and $3.0 Å$, respectively. Calculate the ratio of densities of fcc and bcc.
(1999, 3M)
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Answer:
Correct Answer: 43. $(1.26)$
Solution:
- Density $\propto \dfrac{N}{a^{3}}$
$ \Rightarrow \quad \dfrac{d _1}{d _2}=\dfrac{N _1}{N _2}\left(\dfrac{a _2}{a _1}\right)^{3}=\dfrac{4}{2}\left(\dfrac{3}{3.5}\right)^{3}=1.26 $
BETA
