Question

Two metallic oxides contain 27.6% and 30% oxygen respectively. If the formula of the first oxide is $X_3{O}_4$, the formula of the second will be:

• A. $XO$
• B. $X{O}_2$
• C. $X_2{O}_5$
• D. $X_2{O}_3$

Answer 1

The correct option is D $X_2{O}_3$

$\begin{array}{cc}\text{Oxide-I}& \text{Oxide-II}\\ O=27.6\%& O=30\%\\ X=72.4\%& X=70\%\end{array}$

$72.4\%X=3\text{mol}$ of $X$
$70\%$ of $X$ = $\frac{3}{72.4}\times 70$ = $2.90\text{mol}$ of $X$
Similarly,
$27.6\%$ of $O=4\text{mol}$ of $O$
$30\%$ of $O$ = $\frac{4}{27.6}\times 3$ = 4.34 mol of $O$
$X:O=2.9:4.34\approx 2:3$
Formula of the other oxide will be $X_2{O}_3$