Question

The simplest formula of a compound containing $50$% of element $X$ (Atomic mass $=$ $10$) and $50$% of the element $Y$ (Atomic mass $=$ $20$) by weight is:

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

Answer 1

The correct option is B $X_{2}Y$

$100$ g of sample contains $50$ g of element $X$ and $50$ g of element $Y$.
The atomic masses of elements $X$ and $Y$ are $10$ and $20$ g/mol respectively.
The number of moles of element $X$ present in $50$ g is $\frac{50}{10}=5$
The number of moles of element $Y$ present in $50$ g is $\frac{50}{20}=2.5$
Hence, the mole ratio $X:Y$ is $2:1$
Thus, the simplest formula of a compound containing $50$% of element $X$ and $50$% of the element $Y$ by weight is $X_{2}Y$.