Question

The percentage of element M is 53 in its oxide of molecular formula $M_2O_3$. Its atomic mass is about

• A. 45
• B. 9
• C. 18
• D. 22

Answer 1

Answer: (D)

22

Answer 2

If $m$ is the atomic mass of the element $M$, then $2m + 48\, g$ of $M_{2}O_{3}$ contain $O=48\,g$ $\therefore$ $\%$ of $O$ in $M_{2}O_{3}=\frac{48}{2m+48}\times100=53$ (Given) $\therefore 2m+48=\frac{4800}{53}=90.56$ or $2m=42.56$ or $m=21.28=22$