Semiconducting Devices Question 243
Question: Potassium has a bcc structure with nearest neighbour distance 4.525 Å. Its molecular weight is 39. Its density in kg/m3 is
[DCE 1997]
Options:
A) 900
B) 494
C) 602
D) 802
Show Answer
Answer:
Correct Answer: A
Solution:
Density $ \rho =\frac{nA}{N{{(a)}^{3}}} $ where n = 2 for bcc structure , A = 39 x $10^{-3}$ kg, N = 6.02 x 1023,
a $ =\frac{2}{\sqrt{3}}d=\frac{2}{\sqrt{3}}\times (4.525\times {{10}^{-10}})m $
(d = nearest neighbour distance = distance between centres of two neighbouring atoms $ =\frac{a}{\sqrt{2}} $ )
On putting the values we get r = 907
