Question

A certain compound has the molecular formula, $X_4{O}_6$. If $10$ g of compound contains $5.62$ g of X, the atomic mass of X is approximately :

• A. 32 amu
• B. 30.8 amu
• C. 42 amu
• D. 48 amu

Answer 1

Answer: (B)

30.8 amu

10 g of $X_4{O}_6$ contains $5.62$ g of X.

So, the weight of $O$ is $10-5.62=4.38g$.

Now, as $\frac{weight}{atomicmass}=$ number of atoms in given formula,

So, $\frac{WeightofX}{atomicmassofX}$ : $\frac{WeightofO}{atomicmassofO}=4:6$

Let atomic mass of X be $x$.

$⟹\frac{5.62}{x}$ : $\frac{4.38}{16}=4:6$

$⟹\frac{5.62\times 16}{4.38x}=\frac{4}{6}$

$⟹\frac{5.62\times 16\times 6}{4}=4.38x$

So, $x=30.8amu$.