Bond Enthalpies

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Andre Tsivis 1K
Posts: 16
Joined: Fri Sep 25, 2015 3:00 am

Bond Enthalpies

Postby Andre Tsivis 1K » Thu Jan 28, 2016 6:32 pm

For some reason I can never do these problems properly. For bond enthalpies, do the broken bonds have their values negated or do the formed bonds have their enthalphy negated? Sorry if it's a dumb question but thank you in advance everyone.

Angela Kim 2H
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

Re: Bond Enthalpies

Postby Angela Kim 2H » Thu Jan 28, 2016 10:04 pm

It is the sum of bonds broken minus the sum of bonds formed. It takes energy to break bonds so it would have a positive value. However, when bonds form, they become more stable and thus release energy giving a negative value. Hope this helped!

Chiara R 1K
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

Re: Bond Enthalpies

Postby Chiara R 1K » Thu Jan 28, 2016 10:06 pm

I think in the bond enthalpy problems, broken bonds result in a +H, because heat is needed to break the bond and thus is added to the reaction. Then, forming a bond is the opposite and releases energy, resulting in a -H.

Rex Lee 1C
Posts: 48
Joined: Fri Sep 25, 2015 3:00 am

Bond Enthalpies

Postby Rex Lee 1C » Thu Jan 28, 2016 10:08 pm

Bond enthalpies are the energy required to break a bond, so the bonds that are broken should stay positive, while the bonds that are formed need to be negated (since forming bonds releases energy). The addition of these positive (broken bonds) and negative (formed bonds) values are the ∆H of reaction.


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