Advertisements
Advertisements
Question
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.
Advertisements
Solution
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
RELATED QUESTIONS
How many lattice points are there in one unit cell of the following lattice?
Face-centred cubic
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 ____________.
The arrangement ABC ABC.... is referred to as ____________.
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 |
With the help of a labelled diagram show that there are four octahedral voids per unit cell in a cubic close packed structure.
How can you best describe the elongated octahedral structure of blue vitriol, CuSO4.5H2O?
In the SF4 molecule, there are:
The octane number of Iso-octane is
The crystal system of a compound with unit cell dimensions a = 0.387, b = 0.387 and c = 0.504 nm and α = β = 90° and ϒ = 120° is
Total no. of voids in 0.5 mole of a compound forming hexagonal closed packed structure are:-
The packing efficiency of the two dimensional square unit cell shown below is:
A compound forms hexagonal close-packed structure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids?
Co-ordination number of sodium ion Na+ in Nacl is:-
The right option for the number of tetrahedral and octahedral voids in the hexagonal primitive unit cell is ______.
Element 'B' forms ccp structures and A occupies half of the octahedral voids, while oxygen atoms occupy all the tetrahedral voids. The structure of bimetallic oxide 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)
The density of a pure substance 'X' whose atoms pack in cubic close pack arrangement is 1 g/cc. If all tetrahedral voids are occupied by 'Y' atoms. The value of '3a' is ______ g/cc, if the density of resulting solid is 'a' g/cc.
[Given: Atomic mass (X) = 30 g/mol, (Y) = 20 g/mol]
What fraction of one edge centred octahedral void lies in one unit cell of FCC?
