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Ferric oxide crystallized 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» Given: Oxide (O2-) ions form hcp lattice and ferric (Fe3+) ions occupy 2/3rd of the octahedral voids. To find: Formula of the compound. Calculation: Let the number of oxide ions (O2- ) in hcp unit cell = n \(\therefore\) Number of octahedral voids = n As\(\cfrac{2}{3}\) rd of the octahedral voids are occupied by ferric ions, the number of ferric ions present =n\(\times\frac{2}{3}=\frac{2n}{3}\) \(\therefore\) Ratio of Fe3+ : O2- =\(\frac{2n}{3}:n=2:3\) Ans: The formula of ferric oxide is Fe2O3. |
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