$1.25 \mathrm{~g}$ of a metal (M) reacts with oxygen completely to produce $1.68 \mathrm{~g}$ of metal oxide. The empirical formula of the metal oxide is [molar mass of $\mathrm{M}$ and $\mathrm{O}$ are $69.7 \mathrm{~g} \mathrm{~mol}^{-1}$ and $16.0 \mathrm{~g} \mathrm{~mol}^{-1}$, respectively]

• A

  $\mathrm{M}_{2} \mathrm{O}$
• Correct answer
  B

  $\mathrm{M}_{2} \mathrm{O}_{3}$
• C

  $\mathrm{MO}_{2}$
• D

  $\mathrm{M}_{3} \mathrm{O}_{4}$

Solution

$\Rightarrow \quad \frac{1.25}{\mathrm{E}}=\frac{1.68}{\mathrm{E}+8}$ $\Rightarrow \quad \mathrm{E}=23.25$ $\quad \mathrm{n}-$ factor $=\frac{69.7}{23.25} \approx 3$ $\therefore \quad$ Emprical formula $=\mathrm{M}_{2} \mathrm{O}_{3}$

Hence, the correct answer is option: 'B'.