Question

A metal nitride contains 28% nitrogen by weight. The molecular formula of metal nitride is $M_3{N}_2$. What is the atomic weight of metal ?

• A. 72
• B. 64
• C. 100
• D. 24

Answer 1

The correct option is D 24

100 g of metal nitride will contain 28 g of nitrogen and $100-28=72$ g of metal.
The atomic mass of nitrogen is 14 g/mol.

28 g of nitrogen corresponds to $\frac{28}{14}=2$ moles.

The formula of metal nitride is $M_3{N}_2$.

2 moles of N atoms corresponds to 3 moles of metal.

Hence, 72 g of metal is equal to 3 moles.

The atomic weight of metal is $\frac{72}{3}=24g/mol$.

Hence, option D is correct.