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The same mass of marble reacts with acid faster as a powder than as large chips. Why?
APowder has a larger total mass
BPowder has a larger surface area
CPowder has a higher concentration
DPowder has a higher temperature
Answer & Solution
Correct answer: B. Powder has a larger surface area
1. Only the particles at the surface of a solid can meet the acid.
2. A large lump keeps most of its particles buried inside where the acid cannot reach them.
3. Grinding the same mass into powder exposes far more particles at the surface.
4. More exposed particles means more successful collisions each second, so the rate goes up.
5. The mass is stated to be the same in both cases, so the second option cannot be the reason.
_Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Rate and Extent of Reaction_
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