Question

A crystalline solid is made of two atoms X and Y. Atoms of 'X' are present at the corner while atoms of 'Y' are present at face centres. If one atom of 'X' is missing from the corner, then the simplest formula of the solid is:

• A. $X_7{Y}_{13}$
• B. $X_7{Y}_{24}$
• C. $X_7{Y}_{21}$
• D. $X_6{Y}_7$

Answer 1

The correct option is B $X_7{Y}_{24}$

A crystalline solid is made of two atoms X and Y.

Atoms of 'X' are present at the corner,

so, $X=\frac{8}{8}=1$

Atoms of 'Y' are present at face centres,

$Y=\frac{6}{2}=3$

If one atom of 'X' is missing from the corner,

Now $X=1-\frac{1}{8}=\frac{7}{8}$

The simplest formula of the solid is$=X_{\frac{7}{8}}{Y}_{3}or{X}_7{Y}_{24}$