Question

Two oxides of a metal contain $50$% and $40$% of the metal respectively. The formula of the first oxide is $MO$. The formula of the second oxide is :

• A. $M{O}_2$
• B. $M_2{O}_3$
• C. $M_{2}O$
• D. $M_2{O}_5$

Answer 1

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

100 g of MO contain 50 g metal and 50 g oxygen.
The number of moles of metal and oxygen are same in MO. Hence, the molecular weight of metal is same as that of oxygen. It is 16 g/mol.
100 g of metal oxide contains 40 g of metal and 60 g of oxygen respectively.
60 g of oxygen corresponds to $\frac{60}{18}=3.33$ moles.
40 g of metal corresponds to $\frac{40}{18}=2.22$moles.
Hence, the ratio $M:O$ is $2:3$.
Hence, the formula of the metal oxide is $M_2{O}_3$.