Which factor explains why coal dust is explosive?

• A. Coal dust contains a high percentage of water, which reacts violently.
• B. The dust particles are magnetic, leading to electrical sparks.
• C. Coal dust is highly acidic, causing rapid chemical reactions.
• D. The large surface area of the dust particles increases the rate of combustion.

Answer: (D)

Verified step by step guidance

1. Understand the concept of combustion: Combustion is a chemical reaction between a fuel and oxygen that releases energy in the form of heat and light. For combustion to occur rapidly, factors such as surface area, temperature, and oxygen availability play a significant role.
2. Recognize the role of surface area in chemical reactions: When a substance is broken into smaller particles, its surface area increases. This allows more particles to come into contact with oxygen, which accelerates the rate of the reaction.
3. Relate this to coal dust: Coal dust consists of very fine particles of coal. These fine particles have a much larger surface area compared to a solid chunk of coal of the same mass. This increased surface area allows for rapid and widespread combustion when exposed to oxygen and an ignition source.
4. Eliminate incorrect options: The other options provided (high water content, magnetic properties, and high acidity) do not explain the explosive nature of coal dust. Water would suppress combustion, magnetic properties are unrelated to combustion, and coal dust is not highly acidic.
5. Conclude with the correct explanation: The large surface area of the coal dust particles increases the rate of combustion, making it highly reactive and potentially explosive when dispersed in air and exposed to an ignition source.