Question

$3$ atoms of metal $M$ combine with $2$ atoms of nitrogen to give a compound containing $28\%$ nitrogen and $72\%$ of metal. What is the atomic weight of metal?

• A. 36
• B. 24
• C. 12
• D. 48

Answer 1

Answer: (B)

Formula of the compound must be $M_3{N}_2$

In $100g$ compound, $28g$ nitrogen combines with $72g$ metal.

i.e. $72=3\times$ atomic mass of metal

$\therefore$ Atomic mass of metal $=72/3=24$

Alternatively, $\frac{28}{14}:\frac{72}{x}::2:3$ (Say atomic mass of metal $=x)$

$\frac{72}{x}\times 2=\frac{28}{14}\times 3\Rightarrow x=\frac{72\times 2}{6}=24$