Ferric oxide crystallizes in a hexagonal close packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

Ferric oxide crystallizes in a hexagonal close packed array of oxide i

1.	Ferric oxide crystallizes in a hexagonal close packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.
Answer» Solution :SUPPOSE the number of OXIDE ions `(O^(2-))` in the packing =N `therefore` No. of OCTAHEDRAL voids =n As 2/3rd of the octahedral voids are OCCUPIED by ferric ions, therefore , number of ferric ions present `=2/3xxn="2n"/3` `therefore` Ratio of `Fe^(3+) : O^(2-)="2n"/3 : n=2:3` Hence, the formula of ferric oxide is `Fe_2O_3`