Given
Number of molecules per unit cell, z = 4
Dimensions of unit cell a = 6.8
= 6.8 ×
10−8 cm
b = 4.4
×
10−8 cm
c = 7.2
= 7.2 ×
10−8 cm
Molar mass = 21.76
We have to calculate the density (ρ) of the crystal
Density of the crystal is given as:
ρ =
| z×Molecularweight |
| V×AvogadroNumber |
... (i)
where, z = No of molecules per unit cell
V = Volume = a × b × c
Avogadro's number = 6.023 ×
1023 On substituting all the values In equation (i). we get
ρ =
ρ =
| 4×21.76 |
| 215.×10−22×6.023×1023 |
ρ =
| 87.04 |
| 2.154×10−22×6.023×1023 |
ρ =
ρ =
0.6709gcm−3 Hence, option 'D' is correct.