Question

A crystalline solid XY₃ has ccp arrangement for its element Y. X occupies ...........

(A) 66% of tetrahedral voids

(B) 33% of tetrahedral voids

(C) 66% of octahedral voids

(D) 33% of octahedral voids

Answer 1

Correct answer is: (D) 33% of octahedral voids

The number of particles of Y in ccp unit cell = 4. The formula of the solid is XY₃. Therefore,

the ratio of number of X particles to the number of Y particles is 1 : 3. So, for the unit cell, the

number of X particles = \(\cfrac{4\times 1}{3}\)= 1.33

Number of octahedral voids in ccp unit cell = Number of Y particles in ccp unit cell = 4

\(\therefore\) Percentage of octahedral voids occupied by 

X particles = \(\cfrac{1.33}{4}\times \) 100 = 33%