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Law of conservation of mass

  1. Dec 25, 2016 #1
    Are exothermic reactions violation of law of conservation of mass , because energy and mass are equivalent? Please clarify!!
  2. jcsd
  3. Dec 25, 2016 #2

    Simon Bridge

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    Conservation of mass is a rule of thumb, not a fundamental law. It works because the energy gain or loss in chemical reactions is very small compared with the total mass of the reactants. The mass deficit gets obvious in nuclear reactions. It is total energy that gets conserved.

    [edit]Note: the mass-energy gain or loss in chemical reactions is very small (order parts per billion) compared with the electro-magnetic energy energy change from just rearranging the atoms.
    Last edited: Dec 26, 2016
  4. Dec 26, 2016 #3
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