Question

In an experiment, $4 \,g$ of $ M_{2}O_{x} $ oxide was reduced to $2.8 \,g$ of the metal. If the atomic mass of the metal is $ 56\,g\,mol^{-1}, $ the number of $O$ atoms in the oxide is

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (C)

Mass of oxygen in oxide $=4-2.8$
$=1.2 \,g $
Eq. wt. of metal $=\frac{\text { mass of metal }}{\text { mass of oxygen }} \times 8 $&
$=\frac{2.8}{1.2} \times 8 $
$=18.67$
Valency of metal $=\frac{\text { atomic wt. of metal }}{\text { eq. wt. of metal }}$
$=\frac{56}{18.67} $ (given)
$=3$