Question

Assertion
Mixture of $Ca{C_2}$ and $C{a_3}{P_2}$ placed in the container with holes is thrown into the sea; a luminous flame is produced called Holmes’s signal.
Reason
Both react with ${H_2}O$ :
$Ca{C_2} + 2{H_2}O \to Ca{\left( {OH} \right)_2} + {C_2}{H_2}$
$C{a_3}{P_2} + 6{H_2}O \to 3Ca{\left( {OH} \right)_2} + 2P{H_3}$
Some ${P_2}{H_4}$ is also produced, which catches fire instantly which in turn ignites ${C_2}{H_2}$ (acetylene) and then luminous flame is produced. This guides the approaching ship. The signal is called Holmes’s signal.
$A.$ Both Assertion and reason are correct and reason is the correct explanation for assertion.
$B.$ Both Assertion and reason are correct but reason is not the correct explanation for assertion.
$C.$ Assertion is correct but reason is incorrect.
$D.$ Both Assertion and reason are incorrect.

Answer 1

Hint:Holmes signal is the container containing calcium carbide and calcium phosphide gas. These two gases are placed in a container and thrown in water. Then they produce gases acetylene and phosphine which burn and is served as a signal

Complete answer:
The combustion of phosphine is used in Holmes’s process. It is also used in smoke screens. Mixtures of calcium carbide and calcium phosphide are placed in the container with holes thrown into the sea. When the gases are involved in the sea it serves as a signal. Water enters the container through the holes and reacts to this mixture to give acetylene and phosphine and some amount of diphosphine$\left( {{P_2}{H_4}} \right)$ . Phosphine and phosphine which is produced during the reaction get ignited immediately as it comes in contact with air and also ignites acetylene. Hence, a bright luminous flame is produced which is accompanied by a huge smoke due to the burning of phosphine. This guides the approach ship.
The balance chemical reaction are given below,
$Ca{C_2} + 2{H_2}O \to Ca{\left( {OH} \right)_2} + {C_2}{H_2}$
$C{a_3}{P_2} + 6{H_2}O \to 3Ca{\left( {OH} \right)_2} + 2P{H_3}$
Thus, both the Assertion and reason are correct and reason is the correct explanation for Assertion.

So, the correct option is $A.$
Note:
Gases involved in this question:
Acetylene: Acetylene is the chemical compound with the formula${C_2}{H_2}$. It is a hydrocarbon and the simplest alkyne. This colourless gas is widely used as a fuel and a chemical building block.
Phosphine: phosphine is a colourless, flammable, very toxic gas compound with the chemical formula $P{H_3}$ . Pure phosphine is odourless, but technical grades samples have a highly unpleasant odour like rotting fish, due to the presence of substituted phosphine and diphosphane. Diphosphane is an organic compound which formed in the container is the colourless liquid is one of several binary phosphorus hydrides. It is the impurity that typically causes samples of phosphine to ignite in air.