Question 18
An element with molar mass 2.7 x 10-2kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 x 103 kg m-3, what is the nature of the cubic unit cell?
It is given that density of the element, d = 2.7 ×103 kg m-3
Molar mass, M = 2.7 ×10-2 kg mol-1
Edge length, a= 405 pm = 405 ×10-12 m = 4.05 ×10-10 m
It is known that, Avogadro's number, NA= 6.022 ×1023 mol-1
Applying the relation, This implies that four atoms of the element are present per unit cell. Hence, the unit cell is face-centred cubic (fcc) or cubic close-packed (ccp).
