Question

Which of the following is a component of smoke screens?

• A. Phosphine
• B. Calcium carbide
• C. Copper phosphide
• D. Calcium phosphate

Hint:

Phosphine gas can produce thick white smoke due to formation of phosphorus oxides when exposed to air.

Answer 1

The Correct Option is A

Concept: Smoke screens are used to create dense clouds of smoke for camouflage. Certain chemicals produce thick smoke when they react with air or moisture.

Step 1: Role of phosphine.
Phosphine ($PH_3$) is a gas that can ignite spontaneously in air (due to impurities like diphosphine), producing dense white smoke of phosphorus pentoxide.

Step 2: Analyze options.

• Phosphine → Produces dense smoke (correct)
• Calcium carbide → Produces acetylene gas
• Copper phosphide → Not used for smoke screens
• Calcium phosphate → Stable compound, no smoke formation

Step 3: Final conclusion.
Thus, the component used in smoke screens is: \[ Phosphine \]