Which statement best describes a pyrophoric chemical?

Which statement best describes a pyrophoric chemical?

• A. It ignites spontaneously in air at or below 100
• B. It explodes upon contact with water
• C. It is nonflammable in air
• D. It must be stored under inert gas always

Answer: (A)

Pyrophoric substances ignite spontaneously when they come into contact with air, often at room temperature, without needing an external ignition source. That defining behavior is exactly what the statement describes, making it the best choice because it captures why these chemicals are hazardous and require special handling. The other descriptions either describe different hazards or mix safety practices with the intrinsic property: some materials may react violently with water, which is not what pyrophoric means; being nonflammable in air contradicts the very idea of spontaneous ignition; and storing under inert gas is a safety precaution rather than the fundamental characteristic.

Pyrophoric substances ignite spontaneously when they come into contact with air, often at room temperature, without needing an external ignition source. That defining behavior is exactly what the statement describes, making it the best choice because it captures why these chemicals are hazardous and require special handling. The other descriptions either describe different hazards or mix safety practices with the intrinsic property: some materials may react violently with water, which is not what pyrophoric means; being nonflammable in air contradicts the very idea of spontaneous ignition; and storing under inert gas is a safety precaution rather than the fundamental characteristic.