Editing Joule per mole

{{short description|SI derived unit for energy per amount of material}}

The '''joule per mole''' (symbol: J·mol<sup>−1</sup> or J/mol) is the unit of [[energy]] per [[amount of substance]] in the [[International System of Units]] (SI), such that energy is measured in [[joule]]s, and the amount of substance is measured in [[mole (unit)|moles]]. 

It is also an SI derived unit of molar [[thermodynamic energy]] defined as the energy equal to one joule in one mole of substance.<ref>{{Cite web|title=What does Joule per Mole mean? Definition, meaning and sense|url=https://www.tititudorancea.com/z/joule_per_mole.htm|access-date=2020-06-05|website=www.tititudorancea.com}}</ref><ref>{{Cite web|title=Calorimetry and Molar Enthalpy|url=http://laurenhill.emsb.qc.ca/science/calorimetry.html|access-date=2021-03-05}}</ref> For example, the [[Gibbs free energy]] of a compound in the area of [[thermochemistry]] is often quantified in units of kilojoules per mole (symbol: kJ·mol<sup>−1</sup> or kJ/mol), with 1 kilojoule = 1000 joules.<ref>{{Cite web |title=Units in Thermochemical Calculations – AP Central {{!}} College Board |url=https://apcentral.collegeboard.org/courses/ap-chemistry/classroom-resources/units-in-thermochemical-calculations |access-date=2023-05-21 |website=apcentral.collegeboard.org |language=en}}</ref> 

Physical quantities measured in J·mol<sup>−1</sup> usually describe quantities of energy transferred during [[Phase transition|phase transformations]] or [[chemical reaction]]s. Division by the number of moles facilitates comparison between processes involving different quantities of material and between similar processes involving different types of materials.  The precise meaning of such a quantity is dependent on the context (what substances are involved, circumstances, etc.), but the unit of measurement is used specifically to describe certain existing phenomena, such as in thermodynamics it is the unit of measurement that describes molar energy.<ref>{{Cite book|last=McGlashan|first=M. L.|url=https://books.google.com/books?id=2m8oDwAAQBAJ&q=A+SI+derived+unit+of+molar+thermodynamic+energy+defined+as+the+energy+equal+to+one+joule+in+one+mole+of+substance.&pg=PA49|title=Chemical Thermodynamics: Volume 1|date=2007-10-31|publisher=Royal Society of Chemistry|isbn=978-1-84755-582-3|language=en}}</ref> 

Since there are [[Avogadro constant|6.02214076{{x10^|23}}]] particles (atoms, molecules, ions etc.) per mole, 1 joule per mole is equal to 1 joule multiplied by 6.02214076{{x10^|23}} particles. Because of the typical order of magnitude for energy changes in chemical processes,  kJ·mol<sup>−1</sup> is normally used instead of J·mol<sup>−1</sup>. For example, [[heat of fusion|heats of fusion]] and [[heat of vaporization|vaporization]] are usually of the order of 10 kJ·mol<sup>−1</sup>, [[bond energies]] are of the order of 100 kJ·mol<sup>−1</sup>, and [[ionization energies]] of the order of 1000 kJ·mol<sup>−1</sup>. <ref>{{cite book |last=Schroeder |first=Daniel |date=1999 |title=An Introduction to Thermal Physics |isbn=978-0201380279}}</ref> For this reason, it is common within the field of chemistry to quantify the [[Enthalpy of Reaction|enthalpy of reaction]] in units of kJ·mol<sup>−1</sup>.<ref>{{Cite web |date=2014-11-18 |title=5.4: Enthalpy of Reaction |url=https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/05%3A_Thermochemistry/5.04%3A_Enthalpy_of_Reaction |access-date=2023-05-21 |website=Chemistry LibreTexts |language=en}}</ref>

Other units sometimes used to describe reaction energetics are [[Kilocalorie per mole|kilocalories per mole]] (kcal·mol<sup>−1</sup>), electron volts per particle (eV), and [[wavenumbers]] in inverse centimeters (cm<sup>−1</sup>). 1&nbsp;kJ·mol<sup>−1</sup> is approximately equal to 1.04{{x10^|-2}} [[Electronvolt|eV]] per particle, 0.239&nbsp;[[Kilocalorie per mole|kcal·mol<sup>−1</sup>]], or 83.6&nbsp;cm<sup>−1</sup>. At room temperature (25&nbsp;[[Celsius|°C]], or 298.15&nbsp;[[Kelvin|K]]) 1&nbsp;kJ·mol<sup>−1</sup> is approximately equal to 0.4034&nbsp;[[kT (energy)|<math>k_B T</math>]].

== References ==
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{{DEFAULTSORT:Joule Per Mole}}
[[Category:SI derived units]]
[[Category:Units of chemical measurement]]