Question

In a crystalline solid anions B are arranged in cubic close packing. Cation A are equally distributed between octahedral and tetrahedral voids.If all the octahedral voids are occupied, the formula for solid is

• A. AB
• B. $\text{A}{\text{B}}_{\text{2}}$
• C. ${\text{A}}_{\text{2}}\text{B}$
• D. ${\text{A}}_{\text{2}}{\text{B}}_{\text{3}}$

Answer 1

The correct option is C ${\text{A}}_{\text{2}}\text{B}$

$B$ form $ccp$.

let no. of $B$ is $n$.

$\Rightarrow$ no of octahedral voids $=n$

no. of tetrahedral voids $=2n$

but cation $A$ is equally distributed in Oct. 8 tetr. voids as all Oct. voids are occupied $[i.e.n]$

$80$ cation $A$ is distributed as $n+n(Oct.+tetr.)$

$\frac{B:}{A}=\frac{1n}{2n}$ $B:A::1:2$

Formula is $B{A}_2$ or $A_{2}B$