The superscript degree symbol (°) indicates that substances are in their standard states. Mg(In) solid solution, which was prepared by mechanical alloying, can be reversibly formed by dehydriding from its hydrogenated products (MgH2, MgIn and Mg2In). Copyright © 2011 Acta Materialia Inc. Since enthalpy is a state function, a change in enthalpy does not depend on the pathway between two states. These applications will - due to browser restrictions - send data between your browser and our server. Google use cookies for serving our ads and handling visitor statistics. The Mg(In) solid solution shows decreased reaction enthalpy compared with pure Mg. We use cookies to help provide and enhance our service and tailor content and ads. At constant pressure:    ΔH  = qp    (qp = heat from or to the chemical system at constant pressure,  q is also called heat of reaction), Exothermic reaction:     negative ΔH    (heat transferred to the surroundings from the system), Endothermic reaction:  positive  ΔH    (heat adsorbed by the system from the surroundings). By continuing you agree to the use of cookies. For MgCl2, we must add the enthalpy of formation for Mg (-462.0) to the enthalpy of formation of Cl (-167.4) x 2 because there are two Cl molecules. Parker in National Bureau of Standards (USA) Technical Notes 270-1 to 270-8, 1973. We don't save this data. Cox, DD., Wagman, and V.A. Standard state and enthalpy of formation, Gibbs free energy of formation, entropy and heat capacity, Standard enthalpy of formation, Gibbs free energy of formation, entropy and molar heat capacity of organic substances, Thermodyamics key values internationally agreed, en: standard state enthalpy formation definition value Gibbs free energy entropy molar heat capacity. Enthalpy of fusion: 8.7 kJ mol-1; Enthalpy of vaporisation: 128 kJ mol-1; Enthalpy of atomisation: 146 kJ mol-1; Thermodynamic data. (ΔH°, ΔG°, S°.....). Then it is important to have a common and  well defined reference state. You can reference the WebElements periodic table as follows:"WebElements, https://www.webelements.com, accessed November 2020. You can target the Engineering ToolBox by using AdWords Managed Placements. The specific heat capacity can be calculated from the molar heat capacity, and vise versa: M = molar weight of the actual substance (g/mol). Some of our calculators and applications let you save application data to your local computer. These values are published in a number of places including the WWW (reference 3). For conversion of units, use the Specific heat online unit converter. The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. These tables include heat of formation data gathered from a variety of sources, including the primary and secondary literature, as well as the NIST Chemistry WebBook. These values are published in a number of places including the WWW (reference 3). If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. Most values are those given in the NBS technical notes (reference 1) after conversion from the units used within those notes. Standard state is NOT the same as standard temperature and pressure (STP) for a gas, and must not be confused with this term.Enthalpy is a state function, defined by the internal energy (E), the pressure (P) and volume (V) of a system: For enthalpy, there are no method to determine absolute values, only enthalpy changes (ΔH values) can be measured. This table gives a few thermodynamic data for magnesium. The term standard state is used to describe a reference state for substances, and is a help in thermodynamical calculations (as enthalpy, entropy and Gibbs free energy calculations). Please read AddThis Privacy for more information. AddThis use cookies for handling links to social media. Enthalpy of formation of solid at standard conditions Data from NIST Standard Reference Database 69: NIST Chemistry WebBook The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. chemistry. Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved. Values labelled with an asterisk (*) are Committee on Data for Science and Technology (CODATA) agreed values for the thermodynamic properties of key chemical substances (reference 2). The standard enthalpy of formation of any element in its standard state is zero by definition. Values labelled with an asterisk (*) are Committee on Data for Science and Technology (CODATA) agreed values for the thermodynamic properties of key chemical substances (reference 2). Most values are those given in the NBS technical notes (reference 1) after conversion from the units used within those notes.