Question

$0.28g$ of a nitrogenous compound was subjected to Kjeldahl’s process to produce $0.17g$ of $N{H_3}$. The percentage of nitrogen in the organic compound is
(A) $5$
(B) $2$
(C) $50$
(D) $80$

Answer 1

As we all know that the percentage of any organic compound can be calculated using the given mass of the atom and dividing it by the mass of the compound and multiplying it by $100$.

Complete step by step solution:
As we have learnt that Kjeldahl’s process is a method for the quantitative determination of nitrogen present in an organic compound. The sample is basically heated with sulphuric acid which results in its oxidation and liberation of nitrogen as ammonium sulphate.
Now in the question we are given with $0.28g$ of a nitrogenous compound which produces $0.17g$ of ammonia, using this amount of ammonia we can calculate the mass of nitrogen as we simply know that $17g$ of ammonia has $14g$ of nitrogen, similarly:
$0.17g$of $N{H_3}$ will have $(\dfrac{{14}}{{17}} \times 0.17) = 0.14g$ of nitrogen.
Now, we have the mass of nitrogen and mass of compound so we can calculate the percentage of nitrogen using:
$\% \;of\;Nitrogen = \dfrac{{mass\;of\;nitrogen}}{{mass\;of\;compound}} \times 100 \\\ \Rightarrow \% \;of\;Nitrogen = \dfrac{{0.14}}{{0.28}} \times 100 \\\ \Rightarrow \% \;of\;Nitrogen = 50\% \\\$
Hence, our correct option is (C).

Additional information: Interesting fact about naming of nitrogen:
Jean Antoine Chatpal, a French chemist, names nitrogen as a mineral called niter which contains gas and commonly niter is known as saltpetre or potassium nitrate. It is named as nitrogen azote that means without life.
Liquid nitrogen is widely used as refrigerant to keep the biological microorganisms and organic compounds cold to prevent them from damaging so that they can be used for a long period of time. Liquid nitrogen also freezes skin very immediately when come in contact and can lead to frostbite and other severe damages.

Note: Nitrogen is a colourless, tasteless and odourless gas under normal conditions and makes up approximately $78\%$ of the total air we breathe. It is considered as the most uncombined purest element on Earth.