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The joule per mole (symbol: J·mole−1 or J/mol) is an SI derived unit of energy per amount of material. Energy is measured in joules, and the amount of material is measured in moles. For example, Gibbs free energy is quantified as joules per mole.
SI derived units are units of measurement derived from the seven base units specified by the International System of Units (SI). They are either dimensionless or can be expressed as a product of one or more of the base units, possibly scaled by an appropriate power of exponentiation.
The joule is a derived unit of energy in the International System of Units. It is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre. It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).
The mole is the base unit of amount of substance in the International System of Units (SI). Effective 20 May 2019, the mole is defined as the amount of a chemical substance that contains exactly 6.02214076×1023 (Avogadro constant) constitutive particles, e.g., atoms, molecules, ions or electrons.
Since 1 mole = 6.02214179×1023 particles (atoms, molecules, ions etc.), 1 Joule per mole is equal to 1 Joule divided by 6.02214179×1023 particles, or( 6.022×10^23 particles/mole),1.66054×10−24 Joule per particle. This very small amount of energy is often expressed in terms of a smaller unit such as the electronvolt (eV, see below).
In physics, the electronvolt is a unit of energy equal to approximately 1.6×10−19 joules in SI units.
Physical quantities measured in J·mol−1 usually describe quantities of energy transferred during phase transformations or chemical reactions. 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 meaning of such a quantity is always context-dependent and, particularly for chemical reactions, is dependent on the (possibly arbitrary) definition of a 'mole' for a particular process.
The term phase transition is most commonly used to describe transitions between solid, liquid, and gaseous states of matter, as well as plasma in rare cases. A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change, often discontinuously, as a result of the change of external conditions, such as temperature, pressure, or others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition. Phase transitions commonly occur in nature and are used today in many technologies.
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei, and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.
For convenience and due to the range of magnitudes involved these quantities are almost always reported in kJ·mol−1 rather than in J·mol−1. For example, heats of fusion and vaporization are usually of the order of 10 kJ·mol−1, bond energies are of the order of 100 kJ·mol−1, and ionization energies of the order of 1000 kJ·mol−1.
1 kJ·mol−1 is equal to 0.239 kcal·mol−1 or 1.04×10−2 eV per particle. At room temperature (25 °C, 77 °F, or 298.15 K) 1 kJ·mol−1 is equal to 0.4034 .
The kilocalorie per mole is a unit to measure an amount of energy per number of molecules, atoms, or other similar particles. It is defined as one kilocalorie of energy per one mole of substance, that is, per Avogadro’s number of particles. It is abbreviated "kcal/mol" or "kcal mol−1". As typically measured, one kcal/mol represents a temperature increase of one degree Celsius in one liter of water resulting from the reaction of one mole of reagents.
The Celsius scale, also known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.
The Fahrenheit scale is a temperature scale based on one proposed in 1724 by Dutch–German–Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit as the unit. Several accounts of how he originally defined his scale exist. The lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from equal parts of ice, water and salt. Further limits were established as the melting point of ice (32 °F) and his best estimate of the average human body temperature. The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 °F, and the boiling point of water is defined to be 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure.
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The calorie is a unit of energy. The Calorie is 1,000 calories.
In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton.
Enthalpy, a property of a thermodynamic system, is equal to the system's internal energy plus the product of its pressure and volume. In a system enclosed so as to prevent matter transfer, for processes at constant pressure, the heat absorbed or released equals the change in enthalpy.
Stoichiometry is the calculation of reactants and products in chemical reactions.
In chemistry and physics, activation energy is the energy which must be provided to a chemical or nuclear system with potential reactants to result in: a chemical reaction, nuclear reaction, or various other physical phenomena.
The Avogadro constant, named after scientist Amedeo Avogadro, is the number of constituent particles, usually molecules, atoms or ions that are contained in the amount of substance given by one mole. It is the proportionality factor that relates the molar mass of a substance to the mass of a sample, is designated with the symbol NA or L, and has the value 6.022140857(74)×1023 mol−1 in the International System of Units (SI).
The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states. The standard pressure value p⦵ = 105 Pa (= 100 kPa = 1 bar) is recommended by IUPAC, although prior to 1982 the value 1.00 atm (101.325 kPa) was used. There is no standard temperature. Its symbol is ΔfH⦵. The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature (usually 25 °C or 298.15 K). Standard states are as follows:
The Faraday constant, denoted by the symbol F and sometimes stylized as ℱ, is named after Michael Faraday. In physics and chemistry, this constant represents the magnitude of electric charge per mole of electrons. It has the currently accepted value
Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation or with chemical reaction with another constituent of the solvent, such as acid or alkali. Each type of equilibrium is characterized by a temperature-dependent equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.
In chemistry, the standard molar entropy is the entropy content of one mole of substance under a standard state.
Heat capacity or thermal capacity is a physical quantity equal to the ratio of the heat that is added to an object to the resulting temperature change.
In thermodynamics, the Gibbs free energy is a thermodynamic potential that can be used to calculate the maximum of reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a thermodynamically closed system ; this maximum can be attained only in a completely reversible process. When a system transforms reversibly from an initial state to a final state, the decrease in Gibbs free energy equals the work done by the system to its surroundings, minus the work of the pressure forces.
Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction to transform other chemical substances. Examples include batteries, food, gasoline, and etc. Breaking or making of chemical bonds involves energy, which may be either absorbed or evolved from a chemical system.
kT is the product of the Boltzmann constant, k, and the temperature, T. This product is used in physics as a scale factor for energy values in molecular-scale systems, as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on E / kT. For a system in equilibrium in canonical ensemble, the probability of the system being in state with energy E is proportional to e−ΔE / kT.
Biological thermodynamics is the quantitative study of the energy transductions that occur in or between living organisms, structures, and cells and of the nature and function of the chemical processes underlying these transductions. Biological thermodynamics may address the question of whether the benefit associated with any particular phenotypic trait is worth the energy investment it requires.
In thermodynamics, work performed by a system is energy transferred by the system to its surroundings, due solely to macroscopic forces exerted by the system on its surroundings, where those forces, and their external effects, can be measured. Such work is the only kind by which a thermodynamic system can be made to lift a weight.
This glossary of chemistry terms is a list of terms and definitions relevant to chemistry, including chemical laws, diagrams and formulae, laboratory tools, glassware, and equipment. Chemistry is a physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions; it has an extensive vocabulary and a significant amount of jargon.
This glossary of physics is a list of definitions of terms and concepts relevant to physics, its sub-disciplines, and related fields, including mechanics, materials science, nuclear physics, particle physics, and thermodynamics.