Question

Which is used to produce smoke screens?

• A. Zinc sulphide
• B. Calcium phosphide
• C. Zinc phosphide
• D. Sodium carbonate

Answer 1

Answer: (B)

Calcium phosphide

$P{H}_3$ is formed there along with acetylene under the reaction of $C{a}_3{P}_2$ with $Ca{C}_2$ where , the phosphene reacts with acetylene formed and catches fire to get smoke which forms the smoke screen.

In Holme's singal , the calcium phosphide and calcium carbide is thrown in sea where the reaction produces phosphene gas and acetylene and the phosphene catches fire with acetylene and forms smoke which sends the signal

$C{a}_3{P}_2+6H_O$ $\to$ $3Ca(OH{)}_2$+$2P{H}_3$

$2P{H}_3$ +$4O_2$ $\to$ $P_2{O}_5$+ $3H_{2}O$

$P_2{O}_5$ forms white dense smoke screen.