Question

A binary compound has Y-atoms forming FCC unit cell and another type of X-atoms occupying 1/3rd of tetrahedral voids. Find out the molecular formula of the compound.

• A. XY
• B. X2Y3
• C. X3Y2
• D. XY

Answer 1

Answer: (B)

X2Y3

Answer 2

The correct answer is option (A) : XY

Y-atoms of a binary compound from FCC unit cell.

$\therefore$ No. of Y-atoms per unit = 4

X-atoms of some compounds occupy $\frac{1}{3}rd$ of tetrahedral voids.

No. of X-atoms per unit cell = $\frac{8}{3}$

$\therefore$ the formula of the compound = X$_{\frac{8}{3}}$Y$_4$ as X2Y3