pBlock ElementsII 1 Question 18
18. Extra pure $\mathrm{N} _{2}$ can be obtained by heating
(a) $\mathrm{NH} _{3}$ with $\mathrm{CuO}$
(b) $\mathrm{NH} _{4} \mathrm{NO} _{3}$
(c) $\left(\mathrm{NH} _{4}\right) _{2} \mathrm{Cr} _{2} \mathrm{O} _{7}$
(d) $\mathrm{Ba}\left(\mathrm{N} _{3}\right) _{2}$
(2011)
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Answer:
Correct Answer: 18. (d)
Solution:
- $\mathrm{Ba}\left(\mathrm{N} _{3}\right) _{2} \xrightarrow{\text { Heat }} \mathrm{Ba}(s)+3 \mathrm{N} _{2}(g)$
Azide salt of barium can be obtained in purest form as well as the decomposition product contain solid $\mathrm{Ba}$ as by product alongwith gaseous nitrogen, hence no additional step of separation is required.
Other reactions are
$$ \begin{gathered} \mathrm{NH} _{4} \mathrm{NO} _{3} \xrightarrow{\text { Heat }} \mathrm{N} _{2} \mathrm{O}+2 \mathrm{H} _{2} \mathrm{O} \\ 2 \mathrm{NH} _{3}+3 \mathrm{CuO} \xrightarrow{\text { Heat }} 3 \mathrm{Cu}+3 \mathrm{H} _{2} \mathrm{O}+\mathrm{N} _{2} \\ \left(\mathrm{NH} _{4}\right) _{2} \mathrm{Cr} _{2} \mathrm{O} _{7} \stackrel{\text { Heat }}{\longrightarrow} \mathrm{Cr} _{2} \mathrm{O} _{3}+4 \mathrm{H} _{2} \mathrm{O}+\mathrm{N} _{2} \end{gathered} $$
