CHEM 101A Chapter Notes - Chapter lec 8: Bond-Dissociation Energy, Negative Number, Covalent Bond
18 Oct 2016
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Document Summary
Total energy in the universe remains the same. Reactions that form products having lower potential energy than the reactions are favored. A compound with lower potential energy is more stable than a compound with higher potential energy. Bond breaking always requires an input of energy and bond formation always releases energy. Heat of reactions- when energy is absorbed or released in any reaction. Reported as number of kcal per mole. Also called enthalpy change represented by symbol h. Positive sign when energy is absorbed and negative when it is released. Endothermic h (+): when energy is absorbed. Exothermic h (-): when energy is released. Heat of reaction ( h) for breaking a covalent bond by equally dividing the electrons between two atoms in the bond. Breaking covalent bonds into the atoms it"s composed of is always endothermic. Forming a bond is exothermic and h is a negative number. The stronger the bond, the stronger the bond dissociation energy.
