sblock Elements 2 Question 22
24. Calcium burns in nitrogen to produce a white powder which dissolves in sufficient water to produce a gas $A$ and an alkaline solution. The solution on exposure to air produces a thin solid layer of $B$ on the surface. Identify the compounds $A$ and $B$.
(1996, 3M)
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Solution:
- $A=\mathrm{NH}{3}, B=\mathrm{CaCO}{3}$.
Reactions involved are :
$$ \begin{aligned} & 3 \mathrm{Ca}+\mathrm{N}{2} \xrightarrow{\text { Heat }} \mathrm{Ca}{3} \mathrm{~N}{2} \ & \mathrm{Ca}{3} \mathrm{~N}{2}+6 \mathrm{H}{2} \mathrm{O} \longrightarrow 3 \mathrm{Ca}(\mathrm{OH}){2}+\underset{A}{2 \mathrm{NH}{3}} \ & \mathrm{Ca}(\mathrm{OH}){2}+\underset{\text { (From air) }}{\mathrm{CO}{2}} \longrightarrow \underset{B}{\mathrm{CaCO}{3}}+\mathrm{H}{2} \mathrm{O} \end{aligned} $$
