Question

The percentage composition of a gas is as follow:
Nitrogen $82.35\%$, Hydrogen $17.64\%$.
Find the empirical formula for the gas.

Answer 1

The percentage composition of N and H is given in the question. We know the molecular weight of both N and H. Since it is a ratio of mass, so we have to divide each of them by their respective molecular weights in order to find the moles of N and H and thus we can formulate the empirical formula of the gas.

Complete step by step answer:
Given,
mass of the Nitrogen $= 82.35\%$
mass of the Hydrogen $= 17.64\%$
Molecular weight of Nitrogen = 14, and Molecular weight of Hydrogen = 1
Since this is a ratio of mass, so we have to divide each of them by their respective molecular weights.
Number of moles of nitrogen $= \dfrac{{82.35}}{{14}} = 5.88$
Number of moles of Hydrogen $= \dfrac{{17.64}}{1} = 17.64$
The ratio of their moles is $5.88:17.64 = \dfrac{{5.88}}{{17.64}} = 1:3$
So, $N:H = 1:3$
Thus, the gas is Ammonia $(N{H_3})$
Thus, the empirical formula is $N{H_3}$

Note: Ammonia $(N{H_3})$ is an inorganic compound which is composed of a single nitrogen atom (N) covalently bonded to three hydrogen atoms (H). It is a colourless gas which has a distinct odour. It occurs naturally and is also produced by human activity. Ammonia is an important source of nitrogen that is needed by plants and animals. Ammonia gas can be dissolved in water. This type of ammonia is called liquid ammonia or aqueous ammonia. Liquid ammonia quickly turns into a gas when it is exposed to open air. Ammonia can be applied directly into soil on farm fields, and is also used to make fertilizers for farm crops, lawns, and plants.