What is the formula of a compound in which element P forms ccp lattice and atoms of Q occupy 2/3rd of tetrahedral voids ?

What is the formula of a compound in which element P forms ccp lattice

1.	What is the formula of a compound in which element P forms ccp lattice and atoms of Q occupy 2/3rd of tetrahedral voids ?
Answer» Solution :Suppose oxide ions =n. Then octahedral VOIDS= n. HENCE, `Al^(3+)` ions `=2/3xxn="2N"/3` `therefore` Ratio `Al^(3+) : O^(2-)="2n"/3:n =2:3` , i.e., formula is `Al_2O_3`