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प्रश्न
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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उत्तर
In hexagonal close packing (hcp), the quantity of octahedral voids is equivalent to the number of constituent particles.
Fe3+ ions occupy two thirds of the octahedral voids in ferric oxide, while O2+ ions form the cubic close-packed structure. If there are nO2−ions in the unit cell, the quantity of Fe3+ ions per unit cell would be `(2 n)/3`.
Hence, formula of ferric oxide = `((2 n)/3)` Fe3+ . (n) O2−
= Fe2nO3n
= Fe2O3
संबंधित प्रश्न
A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?
The coordination number of AB having rock salt geometry is ____________.
Hexagonal close packed arrangement of ions is described as ____________.
The arrangement ABC ABC.... is referred to as ____________.
In NaCl structure ____________.
Match the type of packing given in Column I with the items given in Column II.
| Column I | Column II |
| (i) Square close packing in two dimensions |
(a) Triangular voids |
| (ii) Hexagonal close packing in two dimensions |
(b) Pattern of spheres is repeated in every fourth layer |
| (iii) Hexagonal close packing in three dimensions |
(c) Coordination number 4 |
| (iv) Cubic close packing in three dimensions |
(d) Pattern of sphere is repeated in alternate layers |
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The right option for the number of tetrahedral and octahedral voids in hexagonal primitive unit cell is ______.
Ionic radii of cation A+ and anion B- are 102 and 181 pm respectively. These ions are allowed to crystallize into an ionic solid. This crystal has cubic close packing for B-. A+ is present in all octahedral voids. The edge length of the unit cell of the crystal AB is ______ pm. (Nearest integer)
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