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A sealed flask is weighed before and after a reaction inside it. The total mass:
AStays same
BGoes down
CGoes up
DGoes zero
Answer & Solution
Correct answer: A. Stays same
1. Mass can neither be created nor destroyed in a reaction.
2. A sealed flask lets nothing escape.
3. So the total mass stays the same.
_Source: syllabus Science Class IX, Chapter 3, Atoms and Molecules._
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