sblock Elements 1 Question 37
55. Element $A$ burns in nitrogen to give an ionic compound $B$. Compound $B$ reacts with water to give $C$ and $D$. A solution of $C$ becomes ‘milky’ on bubbling carbon dioxide gas. Identify $A, B, C$ and $D$.
(1997, 3M)
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Solution:
- $\quad 3 M+\mathrm{N}{2} \longrightarrow M{3} \mathrm{~N}_{2}$
$M_{3} \mathrm{~N}{2}+6 \mathrm{H}{2} \mathrm{O} \longrightarrow \underset{C}{3 M(\mathrm{OH}){2}}+\underset{D}{2 \mathrm{NH}{3}}$
$M \underset{C}{(\mathrm{OH}){2}}+\mathrm{CO}{2} \longrightarrow \underset{\text { Milkyness }}{M \mathrm{CO}_{3}}$
$M$ can be either $\mathrm{Ca}$ or $\mathrm{Ba}$ but essentially not $\mathrm{Mg}$ because $\mathrm{Mg}(\mathrm{OH})_{2}$ is very sparingly soluble in water.
