Question

A compound contains $28$ percent of nitrogen and $72$ percent of a metal by weight. Three atoms of the metal combine with two atoms of $N$. Find the atomic weight of the metal.

• A. $24$ g
• B. $12$ g
• C. $72$ g
• D. $42$ g

Answer 1

Answer: (A)

$24$ g

$28$ g of nitrogen combines with $72$ g of metal. Three atoms of metal combine with two atoms of nitrogen. This means the valency of metal is $2$.

Let $M$ be the atomic mass of metal.

Equivalents of $N=\frac{28}{\frac{14}{3}}=\frac{1}{6}$

Equivalents of metal $=\frac{72}{\frac{M}{2}}=\frac{144}{M}$

$\frac{1}{6}=\frac{144}{M}$ $\Rightarrow M=\frac{144}{6}=24$ g

Hence, the atomic weight of metal is $24$ g.

Hence, the correct option is $A$