Question

An unknown oxide of manganese is reacted with carbon to form manganese metal and $C{O}_2$. If $31.6g$ of the oxide, $M{n}_x{O}_y$ yielded $13.2g$ of $C{O}_2$ then the simplest formula of the oxide is:
(if atomic mass of $Mn=55u$)

• A. $MnO$
• B. $Mn{O}_2$
• C. $M{n}_2{O}_3$
• D. $M{n}_3{O}_4$

Answer 1

The correct option is C $M{n}_2{O}_3$

According to the question, the balanced reaction would be:
$M{n}_x{O}_y+\frac{y}{2}C\to \frac{y}{2}C{O}_2+x{M}_n$

Given mass of $C{O}_2$ produced = $13.2g$
$\therefore \frac{y}{2}=\frac{13.2}{44}$
$\Rightarrow y=0.6$
Since 1 mole of $M{n}_x{O}_y$ produces $\frac{y}{2}$ moles of $C{O}_2$, thus,
$55x+0.6\times 16=31.6$
$\Rightarrow x=0.4$
$\therefore x:y=2:3$