Question

Average atomic mass of magnesium is $24.31$ a.m.u. This magnesium is composed of $79$ mole $%$ of $^{24}Mg$ and remaining $21$ mole $%$ of $^{24}Mg$ and $^{26}Mg$. Calculate mole $%$ of $^{26}Mg$.

• A. $10$
• B. $11$
• C. $15$
• D. $16$

Answer 1

Answer: (A)

Let mole $%$ of $^{26}Mg$ be $x$
$\therefore \frac{\left(21\,-\,x\right)25\,+\,x\left(26\right)\,+\,79\left(24\right)}{100} = 24.31$
$x = 10\%$