Question

Two elements $P$ (atomic weight $=75$) and $Q$ (atomic weight $=16$) combine to given a compound having $75.8\%$ of $P$. The formula of the compound is

• A. $XY$
• B. $X_{2}Y$
• C. $X{Y}_2$
• D. $X_2{Y}_3$

Answer 1

Answer: (D)

$X_2{Y}_3$

Let total mass of compound be $100g$

So, mass of X become $75.8g$

Mass of Y become $100-75.8$ $=24.2g$

No. of moles of X$=\frac{75.8}{75}\simeq 1$

No.of moles of Y $=\frac{24.2}{16}\simeq 1.5$

Molecular formula of the compound is

$2\times \left(X_1{Y}_{1.5}\right)$ or $X_2{Y}_3$