Question

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.
Find out B

• A. CaO
• B. $CaC{O}_3$
• C. $C{a}_3{N}_2$
• D. None of these

Answer 1

The correct option is B $CaC{O}_3$

Ca burns in air to form CaO and $C{a}_3{N}_2$.
$2Ca+O_2\to 2CaO3Ca+N_2\to C{a}_3{N}_2$
Calcium nitride on hydrolysis with $H_{2}O$ gives ammonia(A)
$C{a}_3{N}_2+6H_{2}O\to 3Ca(OH{)}_2+\underset{\left(A\right)}{2N{H}_3}$
The alkaline solution of $Ca(OH{)}_2$ thus formed reacts with $C{O}_2$ present in the air to form $CaC{O}_3$ (B).
$Ca(OH{)}_2+C{O}_2\to \underset{\left(B\right)}{CaC{O}_3}+H_{2}O$
Thus, $A=N{H}_{3}andB=CaC{O}_3$ (white powder)