Question

Which of the following compound is responsible for catching fire spontaneously in Holme's singal?

• A. $P_2{H}_4$
• B. $P{H}_3$
• C. $C_2{H}_4$
• D. All of these

Answer 1

The correct option is A $P_2{H}_4$

Holme's singal
Containers containing calcium carbide and calcium phosphide are pierced and thrown in the sea when the gases evolved burn and serve as a signal. It is also used in smoke screens.
After making two holes these container are thrown in sea on reacting with water calcium carbide produce scetylene and calcium phosphide produce phosphine,along with phosphine,some amount of $P_2{H}_4$ is also produced,and it catches fire instantly,along with other two gases,luminous flame of acetylene serve as a signal.