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Topic: Theory Help  (Read 177 times)

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Offline ColeHickey_

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Theory Help
« on: November 25, 2020, 03:41:20 AM »
Hi guys, I'm new to this forum. I'm currently studying bond enthalpy and enthalpy change in reactions. I could easily regurgitate out the answers on my test but I hate giving the answers without really understanding the concept. We're told that breaking bonds takes energy and forming bonds releases energy. However for example in an exothermic reaction, where the bond enthalpies of the products are greater than the enthalpies of the reactants, doesn't that mean there is more potential energy stored in the bonds? If more energy is stored in the bonds doesn't that mean energy should be gained overall and thus heat shouldn't be released? Also how does forming a bond even release energy??

Offline mjc123

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Re: Theory Help
« Reply #1 on: November 25, 2020, 05:52:47 AM »
This is a common misconception. Energy is not stored in bonds. A bonded state is an energy minimum; the stronger the bond, the lower the energy. As you say, energy is required to break a bond. Bond enthalpy is the amount of energy required to break a bond - NOT the amount of energy "stored" in a bond.
Have you ever seen an energy-distance diagram for, say, two H atoms?

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