Bond Enthalpies

[Katelyn 2E]

Can someone please explain to me why bond enthalpies (method 2) are always positive? Thank you!

[Emma Li 2C]

Energy is required to break a bond! Like in an endothermic reaction, energy is inputed and so the energy required to break the bonds is positive

[Alvin Tran 2E]

Also, the products side is negative because energy is released when new bonds are formed.

[Anne 2L]

Can someone please explain to me why bond enthalpies (method 2) are always positive? Thank you!

Yea np I gotchu girl! In method 2, the bond enthalpy values given are always positive, because the value given represents the amount of kJ/mol required to break the bond. Since breaking the bond requires energy, the process is endothermic and therefore the enthalpy value is positive.

[Anne 2L]

OH WOW YOU GUYS TYPE FAST.

[Dang Lam]

Because you are breaking the bonds, meaning energy is required and that mean positive value

[Nicole Jacobs 1C]

And vice versa, if you were to add bonds, the reaction would be exothermic because energy is released when bonds are formed. Thus it would be negative if you were talking about the opposite.