Question

Lithium has a bcc structure .Its density is `530 kg m^(-3)` and its atomic mass is `6.94 g mol^(-1)` .Calculate the edge length of a unit cell of lithium metal `(N_(A) = 6.02 xx 10^(23) mol^(-1))`
A. 154pm
B. 352pm
C. 527pm
D. 264pm

Answer 1

Correct Answer - B
`rho=(ZxxM)/(N_(A)xxa^(3))`
For bcc structure
`Z=2.rho=530kg m^(-3)=0.530 g cm^(-1)`
`0.530=(2xx6.94)/(6.02xx10^(23)xxa^(3))`
`a^(3)=4.348xx10^(-23)cm^(3)`
`a=3.52xx10^(-8)`cm
a=352pm