Question

The percentage of an element $M$ is $53$ in its oxide of molecular formula $M_2{O}_3$ . Its atomic mass is about

• A. 45
• B. 9
• C. 18
• D. 36
• E. 27

Answer 1

Answer: (E)

Percentage of element M in $M_2{O}_3=53$
Let the atomic mass of $M=x$
Mass of $M$ in $M_2{O}_3=2x$
Total atomic mass of $M_2{\text{O}}_3=2x+16\times 3$
$=2x+48$ Percentage of an element $=\frac{Massofanelementinacompound}{Totalmassofcompound}\times 100$
$53=\frac{2x}{2x+48}\times 100$
$53(2x+48)=200x$
$x=27$