caluclate the density of a cubic close packing solid having molar mass 63.3g/mol and edge legnth of 288pm (NA= 6.023×10²³)
Answers
Answer:
The number of atoms in a face-centred cubic structure is calculated as:
Number of corners in each cube = g
But each corner atom is shared with 8 other cubes, so its contribution to one cube is (18)th
.
Number of faces in a cube = 6
Each atom on a face-centre is shared by two cubes, therefore, the contribution of each face centred atom is 12
.
Hence, total number of atoms in a cube
= Contribution of corner atoms + Contribution of face - centred atoms
=8×18+6×12=4atoms
Use the formula, =z.MNA.a3
; where d is the density, z is the number of atoms per unit cell, M is the molecular or atomic mass in g/mol, NA
is the Avogadro’s number and ‘a’ is the edge length.
d=4×60×gmol6.022×1023×1mol×(400pm)3×1cm3(1010pm)3
=>d=4×606.022×1023×4003×10−30.gcm3
=>d=6.22gcm−3∼6gcm−3
Therefore the density of the unit cell is 6 gcm−3.