## Bond enthalpies

Simon Dionson 4I
Posts: 107
Joined: Sat Sep 14, 2019 12:17 am

### Bond enthalpies

When calculating a reaction using bond enthalpies, will the answer always be negative (exothermic)?

claudia_1h
Posts: 111
Joined: Fri Aug 09, 2019 12:16 am

### Re: Bond enthalpies

I don't think so, I'm pretty sure if the energy of the bonds broken is greater than the energy of the bonds formed, then the reaction can be endothermic. But someone correct me if I'm wrong.

Ayushi2011
Posts: 101
Joined: Wed Feb 27, 2019 12:17 am

### Re: Bond enthalpies

Breaking a bond is endothermic and forming one is exothermic, so it can be either.

Pegah Nasseri 1K
Posts: 100
Joined: Wed Feb 27, 2019 12:15 am

### Re: Bond enthalpies

No, when calculating enthalpies of a reaction using bond enthalpies you would add up all the enthalpies of the bonds broken along with all the enthalpies of the bonds formed. If the sum of the enthalpies of the bonds broken are greater than the sum of the bonds formed, then the enthalpy of the reaction is positive and the reaction is endothermic. If the sum of the enthalpies of the bonds formed are greater than the sum of the bonds broken, then the enthalpy of the reaction is negative and the reaction is exothermic. This is because breaking a bond requires energy and forming a bond releases energy.

Sally Qiu 2E
Posts: 105
Joined: Fri Aug 30, 2019 12:18 am

### Re: Bond enthalpies

it depends on whether or not the value of bonds formed is greater than that of bonds broken.

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