Q. 193.9( 22 Votes )
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.
Ferric oxide crystalizes in a hexagonal close packed array of oxide ions.
Two out of every three octahedral holes are occupied by ferric ions.
Let the number of oxide ions = x
Since, two out of every three octahedral holes are fitted by ferric ions.
Thus, voids filled by ferric ions
Therefore, number of ferric ions
Now, the ratio of ferric ions to the oxide ions
i.e. Fe3+ : O2- =
= Fe3+ : O2- = = 2 : 3
Thus, formula of ferric oxide is Fe2O3 .
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