Solution :
In an unknown compounds containing $$N$$ and $$H$$
$$\eqalign{
& {\text{given}}\,\,\% \,\,{\text{of}}\,H = 12.5\% \cr
& \therefore \,\,\,\% \,\,{\text{of}}\,N = 100 - 12.5 = 87.5\% \cr} $$
| Element |
Percentage |
Atomic ratio |
Simple ratio |
| $$H$$ |
12.5% |
$$\frac{{12.5}}{1} = 12.5$$ |
$$\frac{{12.5}}{{6.25}} = 2$$ |
| $$N$$ |
87.5 |
$$\frac{{87.5}}{{14}} = 6.25$$ |
$$\frac{{6.25}}{{6.25}} = 1$$ |
$$\eqalign{
& 2 \times {\text{vapour density}} = Mol.\,wt = mol\,wt. \cr
& = 16 \times 2 = 32. \cr
& {\text{Molecular formula}} = n \times {\text{empirical formula}} \cr
& {\text{mass}}\,\,n = \frac{{32}}{{16}} = 2 \cr
& \therefore \,\,{\text{Molecular formula of the compound will be}} \cr
& = {\left( {N{H_2}} \right)_2} = {N_2}{H_4} \cr} $$