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Encyclopedia > Bond dissociation energies

In chemistry, bond dissociation energy, D0, is one measure of the bond strength in a chemical bond. It is defined as the standard enthalpy change when a bond is cleaved by homolysis, with reactants and products of the homolysis reaction at 0K (absolute zero). For instance, the bond dissociation energy for one of the C-H bonds in ethane (C2H6) is defined by the process: Multicolored chemicals are frequent hallmarks of chemistry. ... In chemistry, bond strength is measured between two atoms joined in a chemical bond. ... A chemical bond is the physical phenomenon of chemical substances being held together by attraction of atoms to each other through sharing, as well as exchanging, of electrons -or electrostatic forces. ... Enthalpy (symbolized H, also called heat content) is the sum of the internal energy of matter and the product of its volume multiplied by the pressure. ... In chemistry, homolysis is chemical bond dissociation of a neutral molecule generating two free radicals. ... Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. ... R-phrases S-phrases , , , Flash point -135 °C Autoignition temperature 472 °C Explosive limits 3. ...


CH3CH2-H → CH3CH2 + H


D0 = ΔH = 101.1 kcal/mol


The bond dissociation energy is sometimes also called the bond dissociation enthalpy (or bond enthalpy), but these terms are not strictly correct, as they refer to the above reaction enthalpy at standard conditions, and may differ from D0 by more than 3 kcal/mol. Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ...


The bond dissociation energy is usually different from the bond energy, which is calculated from the sum of the bond dissociation energies of all bonds in a molecule. In chemistry, bond energy (E) is a measure of bond strength in a chemical bond. ... In general, a molecule is the smallest particle of a pure chemical substance that still retains its composition and chemical properties. ...


For example, an O-H bond of a water molecule (H-O-H) has 493.4 kJ mol-1 of bond dissociation energy, and 424.4 kJ mol-1 is needed to cleave the remaining O-H bond. The bond energy of the O-H bonds in water is 458.9 kJ mol-1, which is the average of the values. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... A girl in a swimming pool Water (from the Old English waeter; c. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... A girl in a swimming pool Water (from the Old English waeter; c. ...


Note that following dissociation, if new bonds are formed at lower enthalpy, then there is a net loss of energy, and thus an overall exothermic process. In chemistry, an exothermic reaction is one that releases heat. ...


Heterolytic bond dissociation energy is involved in chemical bond breaking by heterolysis rather than homolysis. In chemistry, heterolysis is chemical bond cleavage of a neutral molecule generating a cation and an anion. ...


See also


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The energy required to cleave a bond homolytically is known as the bond dissociation energy.
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For instance, the bond dissociation energy for one of the C-H bonds in ethane (C
The bond dissociation energy is usually different from the bond energy, which is calculated from the sum of the bond dissociation energies of all bonds in a molecule.
The bond energy of the O-H bonds in water is 458.9 kJ mol
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