Signs in bond enthalpies

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rkang00
Posts: 69
Joined: Fri Sep 28, 2018 12:25 am

Signs in bond enthalpies

Postby rkang00 » Sat Jan 26, 2019 5:27 pm

When putting signs for bond enthalpies, is it usually + on the reactants side and - on the products sign?

emily gao 1C
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

Re: Signs in bond enthalpies

Postby emily gao 1C » Sat Jan 26, 2019 5:51 pm

yes to find the change in enthalpy: do bond energy (reactants) - bond energy (products)

Soumya Ravichandran 4H
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

Re: Signs in bond enthalpies

Postby Soumya Ravichandran 4H » Sat Jan 26, 2019 5:55 pm

Yes, this is because energy is released when bonds are broken, which is what occurs in the reactants. On the other hand, energy is needed to put the bonds back together, which is what occurs in the products.

Porus_Karwa_2E
Posts: 72
Joined: Fri Sep 28, 2018 12:24 am

Re: Signs in bond enthalpies

Postby Porus_Karwa_2E » Sat Jan 26, 2019 7:18 pm

Yes, just add up the enthalpies of prods-reactants

Helen Zhao 1F
Posts: 31
Joined: Fri Sep 28, 2018 12:20 am

Re: Signs in bond enthalpies

Postby Helen Zhao 1F » Sat Jan 26, 2019 7:21 pm

Enthalpy is the total energy in the system. The reactants require energy to break the bonds so the sign is positive when energy goes into the system and because energy is released when bonds form in the products, energy goes out and the sign is negative.


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