Question

A gaseous compound of nitrogen and hydrogen contains $12.5$% by weight of hydrogen. If the density of the compound relative to hydrogen is $16$, the molecular formula of the compound is:

• A. $N{H}_2$
• B. $N{H}_3$
• C. $N{H}_4$
• D. $N_2{H}_4$

Answer 1

Answer: (D)

$N_2{H}_4$

Let the Empirical Formula be $N{H}_x$.
So, $\frac{x}{14+x}\times 100=12.5=>x=2$
Hence, Empirical Formula $=N{H}_2$
Let the Molecular Formula be $N_x{H}_{2x}$.

Now, we know the vapour density of the comound relative to hydrogen which is equal to $\frac{molecularweight}{2}$
$16=\frac{14x+2x}{2}=>x=2$
Therefore, the Molecular formula is $N_2{H}_4$.