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Energy needed to break a bond is equal to the energy given out when bond is formed???

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    • Thread Starter

    I am revising Enthalpy, but this has really thrown me

    My book says that the energy required to break a bond between two atoms is the same amount of energy that is given out when the bond is formed.

    I am fine with the fact that energy is required to break bonds between atoms, but confused as to why it's the same amount of energy given out when the bond was formed

    Does it mean that the (external/heat) energy put into breaking the bond of a molecule is equal to the energy given out from the molecule which it breaks? I just can't picture how energy is given out when a bond is formed, surely when a bond is formed the energy becomes stored as opposed to being released/given out?

    Could anyone please explain to help me better understand this concept?

    Two atoms are bonded to each other. They don't fall apart if you shake one. You have to pull really hard to separate them. Energy must be supplied to break the bond (which means to move the atoms apart to infinite distance).

    When you take two atoms which are an infinite distance apart and let them come together, energy is released. Exactly the same amount of energy has was needed to separate them.

    In loose terms: a strong bond is one that contains little energy, which therefore needs a lot of energy adding to it to break it. And vice versa.
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