1. Tardigrade
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  3. Chemistry
  4. 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. (NA = 6.02 × 1023 mol-1)

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Q. 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. ($NA = 6.02 \times 10^{23} \, mol^{-1}$)

NEETNEET 2016The Solid State

Solution:

For BCC
$d =\frac{Z\times M}{N_{A} \times a^{3}} $
$ 530 = \frac{2 \times6.94 \times10^{-3} }{6.02 \times10^{23} \times a^{3}} $
$ a^{3} = \frac{2 \times694}{530 \times6.23 \times10^{28}} $
$ a^{3} = 0.435 \times10^{-28} m $
$ =43.5 \times10^{-30} m $
$ = 43500000 pm $
$ \therefore a = 352 pm $