Lithium borohydride crystallizes in an orthorhombic system with 4 molecules per unit cell. The unit cell dimensions are a = 6.8Å, b = 4.4Å and C = 7.2Å. If the molar mass is 21.76g. Density of crystal is (gm/cm3)
The correct option is A i.e 0.67
Since
Densiy,ρ = n×molecularweightVolume×Avagadrono.
Here, n = 4, Avagadro no. (NA=6.022×1023)
Volume =a×b ×c
= 6.8×1010−8×4.4×10−8×7.2×10−8cm3
= 2.154×10−22cm3
Densiy,ρ = 4×21.762.154×10−22×6.022×1023 = 0.60708gm/cm3