Question

Ferric oxide is crystallised in hexagonal close packing of oxide ion in which out of three octahedral voids, two are occupied with Fe³⁺ ions. Determine the formula of ferric oxide.

Answer 1

Suppose the number of oxide ions (O^2-) in the packing.
Number of octahedral voids = n
As \(\frac { 2 }{ 3}\)rd of the octahedral voids are occupied by ferric ions, therefore, number of ferric ions present = \(\frac { 2 }{ 3}\) x n = \(\frac { 2n }{ 3}\)
Ratio of Fe³⁺ : O^2-
\(\frac { 2n }{ 3}\) : n= 2:3
Formula of ferric oxide is F₂O₃