1. Tardigrade
  2. Question
  3. Chemistry
  4. Lithium borohydride ( LiBH 4), crystallises in an orthorhombic system with 4 molecules per unit cell. The unit cell dimensions are: a =6.81 A , b =4.43 A , c =717 A. If the molar mass of LiBH 4 is 21.76 g mol -1. The density of the crystal is -

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Q. Lithium borohydride $\left( LiBH _{4}\right)$, crystallises in an orthorhombic system with $4$ molecules per unit cell. The unit cell dimensions are : $a =6.81 A , b =4.43 A , c =717 A$. If the molar mass of $LiBH _{4}$ is $21.76\, g\, mol ^{-1}$. The density of the crystal is -

The Solid State

Solution:

We know that,
$\rho=\frac{Z M}{N V}$
$=\frac{4 \times\left(21.76\, g\, mol ^{-1}\right)}{\left(6.023 \times 10^{23} mol ^{-1}\right)\left(6.81 \times 4.43 \times 7.17 \times 10^{-24} cm ^{3}\right)}$
$=0.668\, g\, cm ^{-3}$