Question

$40ml$ of ammonia gas, taken in an audiometer tube, was subjected to sparks till the volume did not further change. The volume was found to increase by $40ml.40ml$ of oxygen gas then mixed and the mixture was further exploded. The gases remained were $30ml$. Deduce the formula of ammonia. (Ammonia contain $N$ and $H$ only).

Answer 1

Let formula of Ammonia be $NxHy$

$NxHy\to \frac{x}{2}{N}_2+\frac{y}{2}{H}_2$

$\frac{x}{2}\times 40ml+\frac{y}{2}\times 40ml=40+40ml$

$20(x+y)=80$

$x+y=4$ .....(i)

$1mol{H}_2$ required $\frac{1}{2}mol{O}_2$

$\frac{y}{2}mol{H}_2$ required $\frac{y}{4}mol{O}_2$

Amount of $O_2$ left $=40-40\times \frac{Y}{4}$

$=40-10Y$

$40-104+\frac{x}{2}\times 40=30$

$40+20x-10y=30$

$20x-10y=-10$

$2x-y=-1$ ....(ii)

Solve equation (i) and (ii)

we get $x=1y=3$

Formula of Ammonia = $N{H}_3$