Solid State Question 240
Question: Potassium has a $ bcc $ structure with nearest neighbour distance $ 4.52{AA}. $ Its atomic weight is 39. Its density (in $ kg{{m}^{-3}} $ ) will be
[AIIMS 1991]
Options:
A) 454
B) 804
C) 852
D) 908
Show Answer
Answer:
Correct Answer: D
Solution:
For bcc, $ d=\frac{\sqrt{3}}{2}a $ or $ a=\frac{2d}{\sqrt{3}}=\frac{2\times 4.52}{1.732}=5.219\mathring{A}=522pm $
$ \rho =\frac{Z\times M}{a^{3}\times N_0\times {{10}^{-30}}} $
$ =\frac{2\times 39}{{{(522)}^{3}}\times (6.023\times 10^{23})\times {{10}^{-30}}} $
$ =0.91g/cm^{3}=910kg{{m}^{-3}} $
BETA
