Question

A metal oxide contains $70\%$ metal. If atomic weight of the metal is 56, empirical formula of the oxide is:

• A. $M_2{O}_3$
• B. $MO$
• C. $M{O}_2$
• D. $M_3{O}_4$

Answer 1

The correct option is A $M_2{O}_3$

If weight of metal is 70 gm, weight of metal oxide $\to$ 100 gm

If weight of metal is 56 gm (its atomic weight), weight of metal oxide is $\to \frac{100\times 56}{70}=80gm$
and, weight of oxygen $=80-56=24gm$

16 gm corresponds to 1 oxygen atom.

So, for 1 mole of metal, (24/16) moles of oxygen atoms are required. Therefore, for every 16 moles of metal, 24 moles of oxygen is required. In simplest numbers, for every 2 moles of metal, 3 moles of oxygen is required.

Therefore, formula of metal oxide is $M_2{O}_3$.