[dtbcn]

Im reviewing for my ap chem test and a chapter on enthalpy said that when bonds are formed energy is released and when broken, energy is absorbed. I have always thought it was the other way around like when a compound is formed, it absorbs energy and is released when a compound is broken down. Why is it opposite for bond formation?

[Controlled Substance]

It goes both ways. Energy is needed to break bonds, and it is released when it bonds into more stable products. The way you describe it seems to depend on whether those more stable products are the result of creating a compound or breaking one up.

Maybe you are confusing with entropy?

[munchkiness]

sorry to hijack your thread dtbcn,
but seeing your post on bond enthalpy, I was just wondering, why are molar bond enthalpy values always positive?

[Controlled Substance]

Bond enthalpy values are always positive, because like I said, energy is needed to break bonds. Bond enthalpy, aka bond dissociation energy, is the energy it takes to break chemical bonds.

The reason why chemical bonds form in the first place is because the electron configurations of the products result in a lower energy state. To return them to the higher states you must add energy.

[AhmedEzatAlzawalaty]

think how bond forms? for example through a chemical reaction between two compounds
so if the product tends to be more stable ,energy will be released from the more unstable reactants

[dtbcn]

Had to think about it for a while but i understand now. thank you guys.