NEET-XII-Chemistry
exam-1 year:2016
- #65Lithium 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. (NA = 6.02 × ``10^{23} mol^{-1}``)
(1) 154 pm
(2) 352 pm
(3) 527 pm
(4) 264 pmdigAnsr: 2Ans : (2)
Sol.
=
3A
Z M
N a
For bcc structure
Z = 2, = 530 kg m-3 = 0.530 g cm-3
=
23 3
2 6.94
0.530
6.02 10 a
a3 = 4.348 × 10-23 cm3
a = 3.52 × 10-8 cm
a = 352 pm