sblock Elements - Result Question 45
####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:
- $\quad 3 M+N _2 \longrightarrow M _3 N _2$
$M _3 N _2+6 H _2 O \longrightarrow \underset{C}{3 M(OH) _2}+\underset{D}{2 NH _3}$
$M \underset{C}{(OH) _2}+CO _2 \longrightarrow \underset{\text { Milkyness }}{M CO _3}$
$M$ can be either $Ca$ or $Ba$ but essentially not $Mg$ because $Mg(OH) _2$ is very sparingly soluble in water.
