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

Answer: (D)

The explanation for the correct option:

option

(

D)

$X_2{O}_3$

If metallic oxides contain 27.6% and 30% oxygen respectively.
Then, the metallic content X in oxide containing 27.6% is $100-27.6=72.4\%$

And the metallic content X in oxide containing 30% is $100-30=70\%$

Let us calculate the number of moles in it deduce the chemical formula:
$72.4\%X=3\text{mol}$ 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 $O$
$X:O=2.9:4.34\approx 2:3$
Hence, option (D)$X_2{O}_3$ is correct The formula of the other oxide will be $X_2{O}_3$