Question

Oxide ion forming a fcc lattice in which fec 2 + ions are occupying 1 by 8 of tetrahedral void and fe 3 + ions are occupying one by two of the octahedral void what will be the formula of the compound

Answer 1

In CCP lattice of oxide ions, there would be two tetrahedral voids and one octahedral void for each oxide ion. Therefore for four oxide ions, there would be 8 tetrahedral and 4 octahedral voids. Out of 8 tetrahedral voids, 1 is occupied by

A and out of 4 octahedral voids 2 are occupied by B

% of tetrahedral voids occupied by A =begin mathsize 10px style 1 over 8 cross times 100 equals 12.5 % end style

% of octahedral voids occupied by B =begin mathsize 10px style 2 over 4 cross times 100 equals 50 % end style