Question

If the anions (A) form hexagonal closest packing and cations (C) occupy only 2/3 octahedral voids in it, then the general formula of the compound is:

• A. $CA$
• B. $C{A}_2$
• C. $C_2{A}_3$
• D. $C_3{A}_2$

Answer 1

The correct option is C $C_2{A}_3$

In ccp or hcp packing there is one octahedral void corresponding to each atom constituting the close packing. In the compound, only 2/3^rd of the octahedral voids are occupied. It means corresponding to each anion is 2/3 cations. The whole number ratio of A and C in compound is, therefore, 3:2 Hence the formula of the compound is $C_2{A}_3$.