Question

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

• A. 32
• B. 31
• C. 42
• D. 48

Answer 1

The correct option is B 31

Weight of oxygen $=(10-5.62)=4.38gm$

Moles of $O=\frac{4.38}{16}$

Moles of $Xin{X}_4{O}_6=\frac{4.38}{16}\times \frac{2}{3}=\frac{2.92}{16}$

Weight of $X=\frac{2.92}{16}\times M_X=5.62gm$

$\Rightarrow M_X=31gm$