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The bond-dissociation energies of several different bonds of the same type can vary even within a single molecule. For example, a water molecule is composed of two O–H bonds bonded as H–O–H. The bond energy for H 2 O is the average energy required to break each of the two O–H bonds in sequence:
For example, the standard enthalpy of combustion of ethane gas refers to the reaction C 2 H 6 (g) + (7/2) O 2 (g) → 2 CO 2 (g) + 3 H 2 O (l). Standard enthalpy of formation is the enthalpy change when one mole of any compound is formed from its constituent elements in their standard states.
For a homoleptic compound EX n, the E–X bond energy is (1/n) multiplied by the enthalpy change of the reaction EX n → E + nX. Average bond energies given in tables are the average values of the bond energies of a collection of species containing "typical" examples of the bond in question. For example, dissociation of HO−H bond of a water ...
This is true for all enthalpies of formation. The standard enthalpy of formation is measured in units of energy per amount of substance, usually stated in kilojoule per mole (kJ mol −1 ), but also in kilocalorie per mole , joule per mole or kilocalorie per gram (any combination of these units conforming to the energy per mass or amount ...
Enthalpy of atomization is the amount of enthalpy change when bonds of the compound are broken and the component atoms are separated into single atoms ( or monoatom). Enthalpy of atomization is denoted by the symbol ΔH at. The enthalpy change of atomization of gaseous H 2 O is, for example, the sum of the HO–H and H–OH bond dissociation ...
An enthalpy–entropy chart, also known as the H–S chart or Mollier diagram, plots the total heat against entropy, [1] describing the enthalpy of a thermodynamic system. [2] A typical chart covers a pressure range of 0.01–1000 bar , and temperatures up to 800 degrees Celsius . [ 3 ]
A former Tennessee teacher who got pregnant after raping a 12-year-old boy pleaded guilty and has been sentenced to 25 years in prison with no parole. On Dec. 20, Alissa McCommon, 39, of Covington ...
Hess's law is useful in the determination of enthalpies of the following: [2] Heats of formation of unstable intermediates like CO (g) and NO (g). Heat changes in phase transitions and allotropic transitions. Lattice energies of ionic substances by constructing Born–Haber cycles if the electron affinity to form the anion is known, or