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30/12/2021 6:56 pm
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Ferric oxide crystallises 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.
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30/12/2021 7:02 pm
Let the number of oxide (O2-) ions be x.
So, number of octahedral voids = x
It is given that two out of every three octahedral holes are occupied by ferric ions.
So, number of ferric (Fe3+) ions = \(\frac{2}{3}x\)
Therefore, ratio of the number of Fe3+ ions to the number of O2- ions,
Fe3+ : O2- = \(\frac{2}{3}x:x\)
= \(\frac{2}{3}:1\)
= 2:3
Hence, the formula of the ferric oxide is Fe2O3.