Question

Identify A and B in the following reactions:
${\text{Ba}}{{\text{C}}_{\text{2}}}{\text{ + }}{{\text{N}}_{\text{2}}}\xrightarrow{{\text{\Delta }}}{\text{B}}$
${\text{Ca}}{{\text{C}}_{\text{2}}}{\text{ + }}{{\text{N}}_{\text{2}}}\xrightarrow{{\text{\Delta }}}{\text{A}}$
A.${\text{A: Ca(N = C = N) ; B: Ba(C}} \equiv {\text{N)}}$
B.${\text{A: Ca(N - C - N) ; B: B}}{{\text{a}}_{\text{2}}}{{\text{(C}} \equiv {\text{N)}}_{\text{4}}}$
C.${\text{A: Ca(N = C = N}}{{\text{)}}_{\text{2}}}{\text{ ; B: Ba(C}} \equiv {\text{N}}{{\text{)}}_{\text{2}}}$
D.${\text{A: Ca(N - C - N}}{{\text{)}}_{\text{2}}}{\text{ ; B: B}}{{\text{a}}_{\text{2}}}{{\text{(C}} \equiv {\text{N)}}_{\text{4}}}$

Answer 1

Hint: Carbides are prepared at high temperatures in electric arc furnaces. They are mostly formed from oxides reacting with carbon. While nitrogen is an inert gas, in high temperatures it reacts with carbides to form cyanides and cyanamide. The compound formed depends upon the valency of the other element.

Complete step by step answer:
Calcium carbide is formed from the reaction of lime with coke in an electric arc furnace. It is a colourless crystalline solid. Calcium carbide when heated at about ${\text{110}}{{\text{0}}^{\text{o}}}{\text{C}}$ with nitrogen gas for about several hours. Calcium cyanamide is produced. It is then cooled to ambient temperature and purified by leaching. The reaction goes as follows:
${\text{Ca}}{{\text{C}}_{\text{2}}}{\text{ + }}{{\text{N}}_{\text{2}}}\xrightarrow{{\text{Delta }}}{\text{CaC}}{{\text{N}}_{\text{2}}}$
The product formed is present as: ${\text{Ca(N = C = N)}}$ .
Barium carbide is prepared by the reduction of barium carbonate with magnesium in the presence of carbon-14. It can also be prepared by reaction of barium oxide and coke at high temperature. Its properties are similar to calcium carbide, but when exposed to heat barium evaporates leaving behind graphite. When barium carbide is heated with nitrogen gas at high temperatures, it forms barium cyanide. The product is very reactive and reacts with water and carbon dioxide in the air to produce highly toxic hydrogen cyanide gas. The reaction goes as:
${\text{Ba}}{{\text{C}}_{\text{2}}}{\text{ + }}{{\text{N}}_{\text{2}}}\xrightarrow{{\text{Delta }}}{\text{Ba(CN}}{{\text{)}}_{\text{2}}}$
The product is present in the form of ${\text{Ba(C}} \equiv {\text{N}}{{\text{)}}_{\text{2}}}$ .

$\therefore $ The correct option is Option C, i.e. ${\text{A: Ca(N = C = N}}{{\text{)}}_{\text{2}}}{\text{ ; B: Ba(C}} \equiv {\text{N}}{{\text{)}}_{\text{2}}}$ .

Note:
 Calcium cyanamide is also commonly known as nitrolime. It is used as a fertilizer and also in the steelmaking process. Barium cyanide can also be synthesized from hydrogen cyanide and barium hydroxide in water or ether.