Question

The compound used as smoke screen :
(A) $PC{l_3}$
(B) $PC{l_5}$
(C) $P{H_3}$
(D) ${H_3}P{O_3}$

Answer 1

Hint:
A smoke screen is basically a cloud of smoke which is created or released to hinder or restrict the movement of the other party. This smoke screen is generally used by military units. The smoke screen is also released by vehicles.

Complete step by step answer:
Smoke screens are commonly deployed either by a canister (such as a grenade) or generated by a vehicle (such as a tank or a warship).
Whereas smoke screens were originally used to hide movement from enemies ‘line of sight’, modern technology means that they are now also available in new forms, they can screen in the infrared as well as visible spectrum of light to prevent detection by infrared sensor or viewers and they are also available for vehicles in a super dense form used to block loser beams of enemy target designators or range finders.
Definition:
(i) A screen of smoke to hinder enemy observation of a military force, area or activity.
(ii) Something designed to observe, confuse or mislead.
Smoke screen is a compound consists of $P{H_3}$

$P{H_3} + {C_2}{H_2}$ is used as Hole me signals.
Phosphine is also used for making metal phosphides like silver phosphide, copper phosphide.

Additional information:
Phosphine is a trigonal pyramidal molecule with molecular symmetry. The length of all bonds between phosphorus and hydrogen atoms are equivalent. The dipole moment of phosphine increases with the substitution of methyl groups.

Note: Phosphine gas is very toxic which on inhaling causes respiratory irritation, compromises heart and circulatory functions, depresses the central nervous system and produces severe gastrointestinal pain.