Question

The oxide of a metal contains 40% of oxygen. The valency of metal is 2. What is the atomic weight of the metal?

• A. 24
• B. 12
• C. 40
• D. 36

Answer 1

The correct option is A 24

100 g of metal oxide will contain 40 g oxygen and 60 g metal.

Number of moles of oxygen $\frac{40g}{16g/mol}=2.5mol$

The valency of metal is 2. The formula of metal oxide will be MO.

Hence, number of moles of metal $=$ number of moles of oxygen $=2.5mol$

The atomic weight of the metal is-

$\frac{60}{2.5}=24g/mol$.

So, the correct option is $A$