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One basic high school concept problem

  1. Aug 15, 2010 #1
    Very basic (I'm a high school student):

    Background
    I'm studying a chapter in my textbook titled 'Energetics'. It touches on enthalpy changes.
    It mentions that bond-breaking processes are associated with energy absorption and bond-forming processes are assciated with energy emission.

    Question
    Does the theory apply to all bond-breaking and bond-forming reactions?
     
  2. jcsd
  3. Aug 16, 2010 #2

    DrDu

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    Science Advisor

    Yes. "Bonding" means that there is an attractive force between two atoms. Breaking that bond means that you have to do work against this force separating the atoms from its equilibrium distance to a large distance ("infinity"). I.e., you have to do work or invest energy.
     
  4. Aug 18, 2010 #3

    Borek

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    Staff: Mentor

    Note that while this statement (breaking - absorption, forming - emission) is always true, it doesn't state anything abut the final outcome of the reaction. Quite often people confuse these things.

    During each reaction some bonds are broken, others are formed. First step (breaking) requires energy, second step (forming) produces energy.

    Reaction will be exothermic is amount or energy produced in second step is larger than the amount of energy consumed in the first step, or endothermic if you need to put more energy into breaking bonds than you may get from bond creation.

    --
     
  5. Aug 21, 2010 #4
    Thanks very much XD
    I just needed a confirmation.
     
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