View source for Standard enthalpy of formation

{{Short description|Change of enthalpy during the formation of a compound from its elements}}

In [[chemistry]] and [[thermodynamics]], the '''standard enthalpy of formation''' or '''standard heat of formation''' of a [[Chemical compound|compound]] is the change of [[enthalpy]] during the formation of 1 [[mole (unit)|mole]] of the substance from its constituent [[Chemical element|elements in their reference state]], with all substances in their [[standard state]]s. The standard [[pressure]] value {{nowrap|1={{math|''p''{{sup|⦵}}}} = 10{{sup|5}} [[Pascal (unit)|Pa]]}} {{nowrap|1=(= 100 kPa = 1 [[bar (unit)|bar]])}} is recommended by [[IUPAC]], although prior to 1982 the value 1.00 [[atmosphere (unit)|atm]] (101.325 kPa) was used.<ref>{{GoldBookRef| file=S05921 | title = standard pressure}}</ref> There is no standard temperature. Its symbol is Δ<sub>f</sub>''H''<sup>⦵</sup>. The superscript [[Standard state#Typesetting|Plimsoll]] on this symbol indicates that the process has occurred under standard conditions at the specified temperature (usually 25&nbsp;°C or 298.15&nbsp;K).

Standard states are defined for various types of substances. For a gas, it is the hypothetical state the gas would assume if it obeyed the [[ideal gas equation]] at a pressure of 1 bar. For a gaseous or solid [[solute]] present in a diluted [[ideal solution]], the standard state is the hypothetical state of concentration of the solute of exactly one mole per liter (1&nbsp;[[molar concentration|M]]) at a pressure of 1&nbsp;bar extrapolated from infinite dilution. For a pure substance or a [[solvent]] in a condensed state (a liquid or a solid) the standard state is the pure liquid or solid under a pressure of 1&nbsp;bar.

For elements that have multiple [[Allotropy|allotropes]], the reference state usually is chosen to be the form in which the element is most stable under 1&nbsp;bar of pressure. One exception is [[phosphorus]], for which the most stable form at 1&nbsp;bar is [[black phosphorus]], but white phosphorus is chosen as the standard reference state for zero enthalpy of formation.<ref>{{cite book |last1=Oxtoby |first1=David W |url=https://books.google.com/books?id=fJWpg4ZJ2esC&q=standard+exception+white+phosphorus+enthalpy&pg=PA547 |title=Principles of Modern Chemistry |last2=Pat Gillis |first2=H |last3=Campion |first3=Alan |date=2011 |isbn=978-0-8400-4931-5 |page=547|publisher=Cengage Learning }}</ref>

For example, the standard enthalpy of formation of [[carbon dioxide]] is the enthalpy of the following reaction under the above conditions:
:<chem>C(s, graphite) + O2(g) -> CO2(g)</chem>
All elements are written in their standard states, and one mole of product is formed. 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 [[Joule per mole|kilojoule per mole]] (kJ&nbsp;mol<sup>−1</sup>), but also in [[kilocalorie per mole]], [[joule]] per mole or kilocalorie per [[gram (unit)|gram]] (any combination of these units conforming to the energy per mass or amount guideline).

All elements in their reference states ([[oxygen]] gas, solid [[carbon]] in the form of [[graphite]], etc.) have a standard enthalpy of formation of zero, as there is no change involved in their formation.

The formation reaction is a constant pressure and constant temperature process. Since the pressure of the standard formation reaction is fixed at 1 bar, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a single temperature: 298&nbsp;K, represented by the symbol {{math|Δ{{sub|f}}''H''{{su|b=298 K|p=⦵}}}}.

== Hess' law ==
For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The [[enthalpy of reaction]] can then be analyzed by applying [[Hess' law]], which states that the ''sum'' of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction. This is true because enthalpy is a [[state function]], whose value for an overall process depends only on the initial and final states and not on any intermediate states. Examples are given in the following sections.

== Ionic compounds: Born–Haber cycle ==
[[File:Born-haber cycle LiF.svg|450px|thumb|Standard enthalpy change of formation in [[Born–Haber cycle|Born–Haber]] diagram for [[lithium fluoride]]. {{math|Δ{{sub|latt}}''H''}} corresponds to {{math|U{{sub|L}}}} in the text. The downward arrow "electron affinity" shows the negative quantity {{math|–EA{{sub|F}}}}, since {{math|EA{{sub|F}}}} is usually [[Electron affinity#Sign convention|defined as positive.]]]]
For ionic compounds, the standard enthalpy of formation is equivalent to the sum of several terms included in the [[Born–Haber cycle]]. For example, the formation of [[lithium fluoride]],

:<chem>Li(s) + 1/2 F2(g) -> LiF(s)</chem>

may be considered as the sum of several steps, each with its own enthalpy (or energy, approximately): 
# {{math|''H''{{sub|sub}}}}, the [[standard enthalpy of atomization]] (or [[Sublimation (phase transition)|sublimation]]) of solid lithium.
# {{math|IE{{sub|Li}}}}, the [[first ionization energy]] of gaseous lithium.
# {{math|B(F–F)}}, the standard [[enthalpy of atomization]] (or bond energy) of fluorine gas.
# {{math|EA{{sub|F}}}}, the [[electron affinity]] of a fluorine atom.
# {{math|U{{sub|L}}}}, the [[lattice energy]] of lithium fluoride.

The sum of these enthalpies give the standard enthalpy of formation ({{math|&Delta;{{sub|f}}''H''}}) of lithium fluoride:

:<math>\Delta H_\text{f} = \Delta H_\text{sub} + \text{IE}_\text{Li} + \frac{1}{2}\text{B(F–F)} - \text{EA}_\text{F} + \text{U}_\text{L}.</math>

In practice, the enthalpy of formation of lithium fluoride can be determined experimentally, but the lattice energy cannot be measured directly. The equation is therefore rearranged to evaluate the lattice energy:<ref>Moore, Stanitski, and Jurs. ''Chemistry: The Molecular Science''. 3rd edition. 2008.  {{ISBN|0-495-10521-X}}. pages 320–321.</ref>

:<math>-U_\text{L} = \Delta H_\text{sub} + \text{IE}_\text{Li} + \frac{1}{2}\text{B(F–F)} - \text{EA}_\text{F} - \Delta H_\text{f}.</math>

==Organic compounds==
The formation reactions for most organic compounds are hypothetical. For instance, carbon and hydrogen will not directly react to form [[methane]] ({{chem2|CH4}}), so that the standard enthalpy of formation cannot be measured directly. However the [[Heat of combustion|standard enthalpy of combustion]] is readily measurable using [[Calorimeter#Bomb calorimeters|bomb calorimetry]]. The standard enthalpy of formation is then determined using [[Hess's law]]. The combustion of methane:
:<chem>CH4 + 2 O2 -> CO2 + 2 H2O</chem>
is equivalent to the sum of the hypothetical decomposition into elements followed by the combustion of the elements to form [[carbon dioxide]] ({{chem2|CO2}}) and water ({{chem2|H2O}}):
:<chem>CH4 -> C + 2H2</chem>
:<chem>C + O2 -> CO2</chem>
:<chem>2H2 + O2 -> 2H2O</chem>

Applying Hess's law, 
:<math>\Delta_\text{comb} H^\ominus ( \text{CH}_4 ) = [ \Delta_\text{f} H^\ominus (\text{CO}_2) + 2 \Delta_\text{f} H^\ominus ( \text{H}_2 \text{O} ) ] - \Delta_\text{f} H^\ominus (\text{CH}_4).</math>

Solving for the standard of enthalpy of formation,
:<math>\Delta_\text{f} H^\ominus (\text{CH}_4) = [ \Delta_\text{f} H^\ominus (\text{CO}_2) + 2 \Delta_\text{f} H^\ominus (\text{H}_2 \text{O})] - \Delta_\text{comb} H^\ominus (\text{CH}_4).</math>

The value of {{tmath|\Delta_\text{f} H^\ominus (\text{CH}_4)}} is determined to be −74.8&nbsp;kJ/mol. The negative sign shows that the reaction, if it were to proceed, would be [[exothermic]]; that is, methane is enthalpically more stable than hydrogen gas and carbon.

It is possible to predict heats of formation for simple [[Strain (chemistry)|unstrained]] organic compounds with the [[heat of formation group additivity]] method.

== Use in calculation for other reactions ==
The [[Standard enthalpy of reaction|standard enthalpy change of any reaction]] can be calculated from the standard enthalpies of formation of reactants and products using Hess's law. A given reaction is considered as the decomposition of all reactants into elements in their standard states, followed by the formation of all products. The heat of reaction is then ''minus'' the sum of the standard enthalpies of formation of the reactants (each being multiplied by its respective stoichiometric coefficient, {{mvar|ν}}) ''plus'' the sum of the standard enthalpies of formation of the products (each also multiplied by its respective stoichiometric coefficient), as shown in the equation below:<ref>{{cite web|url=http://www.science.uwaterloo.ca/~cchieh/cact/c120/heatreac.html|title=Enthalpies of Reaction|website=www.science.uwaterloo.ca|access-date=2 May 2018|url-status=live|archive-url=https://web.archive.org/web/20171025201240/http://www.science.uwaterloo.ca/~cchieh/cact/c120/heatreac.html|archive-date=25 October 2017}}</ref>

:<math>\Delta_{\text{r}} H^{\ominus } = \sum \nu \Delta_{\text{f}} H^{\ominus }(\text{products}) - \sum \nu \Delta_{\text{f}} H^{\ominus}(\text{reactants}).</math>

If the standard enthalpy of the products is less than the standard enthalpy of the reactants, the standard enthalpy of reaction is negative. This implies that the reaction is exothermic. The converse is also true; the standard enthalpy of reaction is positive for an endothermic reaction. This calculation has a tacit assumption of [[ideal solution]] between reactants and products where the [[enthalpy of mixing]] is zero.

For example, for the combustion of methane, <chem>CH4 + 2O2 -> CO2 + 2H2O</chem>:

:<math>\Delta_{\text{r}} H^{\ominus } = [\Delta_{\text{f}} H^{\ominus }(\text{CO}_2) + 2\Delta_{\text{f}} H^{\ominus } (\text{H}_2{}\text{O})] - [\Delta_{\text{f}} H^{\ominus }(\text{CH}_4) + 2\Delta_{\text{f}} H^{\ominus }(\text{O}_2)].</math>
However <chem>O2</chem> is an element in its standard state, so that <math> \Delta_{\text{f}} H^{\ominus }(\text{O}_2) = 0</math>, and the heat of reaction is simplified to 
:<math>\Delta_{\text{r}} H^{\ominus } = [\Delta_{\text{f}} H^{\ominus }(\text{CO}_2) + 2\Delta_{\text{f}} H^{\ominus } (\text{H}_2{}\text{O})] - \Delta_{\text{f}} H^{\ominus }(\text{CH}_4),</math>
which is the equation in the previous section for the enthalpy of combustion <math>\Delta_{\text{comb}}H^{\ominus }</math>.

== Key concepts for enthalpy calculations ==
*When a reaction is reversed, the magnitude of Δ''H'' stays the same, but the sign changes.
*When the balanced equation for a reaction is multiplied by an integer, the corresponding value of Δ''H'' must be multiplied by that integer as well.
*The change in enthalpy for a reaction can be calculated from the enthalpies of formation of the reactants and the products
*Elements in their standard states make no contribution to the enthalpy calculations for the reaction, since the enthalpy of an element in its standard state is zero. [[Allotropy|Allotropes]] of an element other than the standard state generally have non-zero standard enthalpies of formation.

== Examples: standard enthalpies of formation at 25&nbsp;°C ==
Thermochemical properties of selected substances at 298.15&nbsp;K and 1&nbsp;atm

===Inorganic substances===
{{sticky header}}
{| class="wikitable sortable sticky-header"
|-
! Species
! Phase
! Chemical formula
! data-sort-type=number| Δ<sub>f</sub>''H''<sup>⦵</sup> /(kJ/mol)
|-
| [[Aluminium]]
| Solid
| Al
| 0
|-
| [[Aluminium chloride]]
| Solid
| AlCl<sub>3</sub>
| −705.63
|-
| [[Aluminium oxide]]
| Solid
| Al<sub>2</sub>O<sub>3</sub>
| −1675.5
|-
| [[Aluminium hydroxide]]
| Solid
| Al(OH)<sub>3</sub>
| −1277
|-
| [[Aluminium sulphate]]
| Solid
| Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>
| −3440
|-
| [[Barium chloride]]
| Solid
| BaCl<sub>2</sub>
| −858.6
|-
| [[Barium carbonate]]
| Solid
| BaCO<sub>3</sub>
| −1216
|-
| [[Barium hydroxide]]
| Solid
| Ba(OH)<sub>2</sub>
| −944.7
|-
| [[Barium oxide]]
| Solid
| BaO
| −548.1
|-
| [[Barium sulfate]]
| Solid
| BaSO<sub>4</sub>
| −1473.3
|-
| [[Beryllium]]
| Solid
| Be
| 0
|-
| [[Beryllium hydroxide]]
| Solid
| Be(OH)<sub>2</sub>
| −903
|-
| [[Beryllium oxide]]
| Solid
| BeO
| −609.4
|-
| [[Boron trichloride]]
| Solid
| BCl<sub>3</sub>
| −402.96
|-
| [[Bromine]]
| Liquid
| Br<sub>2</sub>
| 0
|-
| [[Bromide ion]]
| Aqueous
| Br<sup>−</sup>
| −121
|-
| [[Bromine]]
| Gas
| Br
| 111.884
|-
| [[Bromine]]
| Gas
| Br<sub>2</sub>
| 30.91
|-
| [[Bromine trifluoride]]
| Gas
| BrF<sub>3</sub>
| −255.60
|-
| [[Hydrogen bromide]]
| Gas
| HBr
| −36.29
|-
| [[Cadmium]]
| Solid
| Cd
| 0
|-
| [[Cadmium oxide]]
| Solid
| CdO
| −258
|-
| [[Cadmium hydroxide]]
| Solid
| Cd(OH)<sub>2</sub>
| −561
|-
| [[Cadmium sulfide]]
| Solid
| CdS
| −162
|-
| [[Cadmium sulfate]]
| Solid
| CdSO<sub>4</sub>
| −935
|-
| [[Caesium]]
| Solid
| Cs
| 0
|-
| [[Caesium]]
| Gas
| Cs
| 76.50
|-
| [[Caesium]]
| Liquid
| Cs
| 2.09
|-
| Caesium(I) ion
| Gas
| Cs<sup>+</sup>
| 457.964
|-
| [[Caesium chloride]]
| Solid
| CsCl
| −443.04
|-
| [[Calcium]]
| Solid
| Ca
| 0
|-
| [[Calcium]]
| Gas
| Ca
| 178.2
|-
| Calcium(II) ion
| Gas
| Ca<sup>2+</sup>
| 1925.90
|-
| Calcium(II) ion
| Aqueous
| Ca<sup>2+</sup>
| −542.7
|-
| [[Calcium carbide]]
| Solid
| CaC<sub>2</sub>
| −59.8
|-
| [[Calcium carbonate]] ([[Calcite]])
| Solid
| CaCO<sub>3</sub>
| −1206.9
|-
| [[Calcium chloride]]
| Solid
| CaCl<sub>2</sub>
| −795.8
|-
| [[Calcium chloride]]
| Aqueous
| CaCl<sub>2</sub>
| −877.3
|-
| [[Calcium phosphate]]
| Solid
| Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>
| −4132
|-
| [[Calcium fluoride]]
| Solid
| CaF<sub>2</sub>
| −1219.6
|-
| [[Calcium hydride]]
| Solid
| CaH<sub>2</sub>
| −186.2
|-
| [[Calcium hydroxide]]
| Solid
| Ca(OH)<sub>2</sub>
| −986.09
|-
| [[Calcium hydroxide]]
| Aqueous
| Ca(OH)<sub>2</sub>
| −1002.82
|-
| [[Calcium oxide]]
| Solid
| CaO
| −635.09
|-
| [[Calcium sulfate]]
| Solid
| CaSO<sub>4</sub>
| −1434.52
|-
| [[Calcium sulfide]]
| Solid
| CaS
| −482.4
|-
| [[Wollastonite]]
| Solid
| CaSiO<sub>3</sub>
| −1630
|-
| [[Carbon]] ([[Graphite]])
| Solid
| C
| 0
|-
| [[Carbon]] ([[Diamond]])
| Solid
| C
| 1.9
|-
| [[Carbon]]
| Gas
| C
| 716.67
|-
| [[Carbon dioxide]]
| Gas
| CO<sub>2</sub>
| −393.509
|-
| [[Carbon disulfide]]
| Liquid
| CS<sub>2</sub>
| 89.41
|-
| [[Carbon disulfide]]
| Gas
| CS<sub>2</sub>
| 116.7
|-
| [[Carbon monoxide]]
| Gas
| CO
| −110.525
|-
| [[Carbonyl chloride]] ([[Phosgene]])
| Gas
| COCl<sub>2</sub>
| −218.8
|-
| Carbon dioxide (un–ionized)
| Aqueous
| CO<sub>2</sub>(aq)
| −419.26
|-
| [[Bicarbonate]] ion
| Aqueous
|HCO<sub>3</sub><sup>–</sup>
| −689.93
|-
| [[Carbonate]] ion
| Aqueous
|CO<sub>3</sub><sup>2–</sup>
| −675.23
|-
| Monatomic chlorine
| Gas
| Cl
| 121.7
|-
| [[Chloride]] ion
| Aqueous
| Cl<sup>−</sup>
| −167.2
|-
| [[Chlorine]]
| Gas
| Cl<sub>2</sub>
| 0
|-
| [[Chromium]]
| Solid
| Cr
| 0
|-
| [[Copper]]
| Solid
| Cu
| 0
|-
| [[Copper(II) bromide]]
| Solid
| CuBr2
| −138.490
|-
| [[Copper(II) chloride]]
| Solid
| CuCl2
| −217.986
|-
| [[Copper(II) oxide]]
| Solid
| CuO
| −155.2
|-
| [[Copper(II) sulfate]] || Aqueous
|| CuSO<sub>4</sub> || −769.98
|-
| [[Fluorine]]
| Gas
| F<sub>2</sub>
| 0
|-
| Monatomic hydrogen
| Gas
| H
| 218
|-
| [[Hydrogen]]
| Gas
| H<sub>2</sub>
| 0
|-
| [[Water]]
| Gas
| H<sub>2</sub>O
| −241.818
|-
| [[Water]]
| Liquid
| H<sub>2</sub>O
| −285.8
|-
| [[Hydrogen ion]]
| Aqueous
| H<sup>+</sup>
| 0
|-
| [[Hydroxide ion]]
| Aqueous
| OH<sup>−</sup>
| −230
|-
| [[Hydrogen peroxide]]
| Liquid
| H<sub>2</sub>O<sub>2</sub>
| −187.8
|-
| [[Phosphoric acid]]
| Liquid
| H<sub>3</sub>PO<sub>4</sub>
| −1288
|-
| [[Hydrogen cyanide]]
| Gas
| HCN
| 130.5
|-
| [[Hydrogen bromide]]
| Liquid
| HBr
| −36.3
|-
| [[Hydrogen chloride]]
| Gas
| HCl
| −92.30
|-
| [[Hydrogen chloride]]
| Aqueous
| HCl
| −167.2
|-
| [[Hydrogen fluoride]]
| Gas
| HF
| −273.3
|-
| [[Hydrogen iodide]]
| Gas
| HI
| 26.5
|-
| [[Iodine]]
| Solid
| I<sub>2</sub>
| 0
|-
| [[Iodine]]
| Gas
| I<sub>2</sub>
| 62.438
|-
| [[Iodine]]
| Aqueous
| I<sub>2</sub>
| 23
|-
| [[Iodide]] ion
| Aqueous
| I<sup>−</sup>
| −55
|-
| [[Iron]]
| Solid
| Fe
| 0
|-
| Iron carbide ([[Cementite]])
| Solid
| Fe<sub>3</sub>C
| 5.4
|-
| Iron(II) carbonate ([[Siderite]])
| Solid
| FeCO<sub>3</sub>
| −750.6
|-
| [[Iron(III) chloride]]
| Solid
| FeCl<sub>3</sub>
| −399.4
|-
| [[Iron(II) oxide]] ([[Wüstite]])
| Solid
| FeO
| −272
|-
| [[Iron(II,III) oxide]] ([[Magnetite]])
| Solid
| Fe<sub>3</sub>O<sub>4</sub>
| −1118.4
|-
| [[Iron(III) oxide]] ([[Hematite]])
| Solid
| Fe<sub>2</sub>O<sub>3</sub>
| −824.2
|-
| [[Iron(II) sulfate]]
| Solid
| FeSO<sub>4</sub>
| −929
|-
| [[Iron(III) sulfate]]
| Solid
| Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>
| −2583
|-
| [[Iron(II) sulfide]]
| Solid
| FeS
| −102
|-
| [[Pyrite]]
| Solid
| FeS<sub>2</sub>
| −178
|-
| [[Lead]]
| Solid
| Pb
| 0
|-
| [[Lead dioxide]]
| Solid
| PbO<sub>2</sub>
| −277
|-
| [[Lead sulfide]]
| Solid
| PbS
| −100
|-
| [[Lead sulfate]]
| Solid
| PbSO<sub>4</sub>
| −920
|-
| [[Lead(II) nitrate]]
| Solid
| Pb(NO<sub>3</sub>)<sub>2</sub>
| −452
|-
| [[Lead(II) sulfate]]
| Solid
| PbSO<sub>4</sub>
| −920
|-
| [[Lithium fluoride]]
| Solid
| LiF
| −616.93
|-
| [[Magnesium]]
| Solid
| Mg
| 0
|-
| Magnesium ion
| Aqueous
| Mg<sup>2+</sup>
| −466.85
|-
| [[Magnesium carbonate]]
| Solid
| MgCO<sub>3</sub>
| −1095.797
|-
| [[Magnesium chloride]]
| Solid
| MgCl<sub>2</sub>
| −641.8
|-
| [[Magnesium hydroxide]]
| Solid
| Mg(OH)<sub>2</sub>
| −924.54
|-
| [[Magnesium hydroxide]]
| Aqueous
| Mg(OH)<sub>2</sub>
| −926.8
|-
| [[Magnesium oxide]]
| Solid
| MgO
| −601.6
|-
| [[Magnesium sulfate]]
| Solid
| MgSO<sub>4</sub>
| −1278.2
|-
| [[Manganese]]
| Solid
| Mn
| 0
|-
| [[Manganese(II) oxide]]
| Solid
| MnO
| −384.9
|-
| [[Manganese(IV) oxide]]
| Solid
| MnO<sub>2</sub>
| −519.7
|-
| [[Manganese(III) oxide]]
| Solid
| Mn<sub>2</sub>O<sub>3</sub>
| −971
|-
| [[Manganese(II,III) oxide]]
| Solid
| Mn<sub>3</sub>O<sub>4</sub>
| −1387
|-
| [[Permanganate]]
| Aqueous
| {{chem|MnO|4|−}}
| −543
|-
| [[Mercury(II) oxide]] (red)
| Solid
| HgO
| −90.83
|-
| [[Mercury sulfide]] (red, [[cinnabar]])
| Solid
| HgS
| −58.2
|-
| [[Nitrogen]]
| Gas
| N<sub>2</sub>
| 0
|-
| [[Ammonia]] (ammonium hydroxide) || Aqueous
|| NH<sub>3</sub> (NH<sub>4</sub>OH) || −80.8
|-
| Ammonia || Gas
|| NH<sub>3</sub> || −46.1
|-
| [[Ammonium nitrate]] || Solid
|| NH<sub>4</sub>NO<sub>3</sub> || −365.6
|-
| [[Ammonium chloride]]
| Solid
| NH<sub>4</sub>Cl
| −314.55
|-
| [[Nitrogen dioxide]]
| Gas
| NO<sub>2</sub>
| 33.2
|-
| [[Hydrazine]]
| Gas
| N<sub>2</sub>H<sub>4</sub>
| 95.4
|-
| [[Hydrazine]]
| Liquid
| N<sub>2</sub>H<sub>4</sub>
| 50.6
|-
| [[Nitrous oxide]]
| Gas
| N<sub>2</sub>O
| 82.05
|-
| [[Nitric oxide]]
| Gas
| NO
| 90.29
|-
| [[Dinitrogen tetroxide]]
| Gas
| N<sub>2</sub>O<sub>4</sub>
| 9.16
|-
| [[Dinitrogen pentoxide]]
| Solid
| N<sub>2</sub>O<sub>5</sub>
| −43.1
|-
| [[Dinitrogen pentoxide]]
| Gas
| N<sub>2</sub>O<sub>5</sub>
| 11.3
|-
|[[Nitric acid]]
|Aqueous
|HNO<sub>3</sub>
|−207
|-
|Monatomic oxygen
|Gas
|O
|249
|-
|[[Oxygen]]
|Gas
|O<sub>2</sub>
|0
|-
|[[Ozone]]
|Gas
|O<sub>3</sub>
|143
|-
| [[White phosphorus]]
| Solid
| P<sub>4</sub>
| 0
|-
| [[Red phosphorus]]
| Solid
| P
| −17.4<ref name=HS>{{Housecroft2nd|page=392}}</ref>
|-
| [[Black phosphorus]]
| Solid
| P
| −39.3<ref name=HS/>
|-
| [[Phosphorus trichloride]]
| Liquid
| PCl<sub>3</sub>
| −319.7
|-
| [[Phosphorus trichloride]]
| Gas
| PCl<sub>3</sub>
| −278
|-
| [[Phosphorus pentachloride]]
| Solid
| PCl<sub>5</sub>
| −440
|-
| [[Phosphorus pentachloride]]
| Gas
| PCl<sub>5</sub>
| −321
|-
| [[Phosphorus pentoxide]]
| Solid
| P<sub>2</sub>O<sub>5</sub>
| −1505.5<ref>{{cite book |editor1-last=Green |editor1-first=D.W. |title=Perry's Chemical Engineers' Handbook |date=2007 |publisher=Mcgraw-Hill |isbn=9780071422949 |pages=2–191 |edition=8th |ref=P2O5}}</ref>
|-
| [[Potassium bromide]]
| Solid
| KBr
| −392.2
|-
| [[Potassium carbonate]]
| Solid
| K<sub>2</sub>CO<sub>3</sub>
| −1150
|-
| [[Potassium chlorate]]
| Solid
| KClO<sub>3</sub>
| −391.4
|-
| [[Potassium chloride]]
| Solid
| KCl
| −436.68
|-
| [[Potassium fluoride]]
| Solid
| KF
| −562.6
|-
| [[Potassium oxide]]
| Solid
| K<sub>2</sub>O
| −363
|-
| [[Potassium nitrate]]
| Solid
| KNO<sub>3</sub>
| −494.5
|-
| [[Potassium perchlorate]]
| Solid
| KClO<sub>4</sub>
| −430.12
|-
| [[Silicon]]
| Gas
| Si
| 368.2
|-
| [[Silicon carbide]]
| Solid
| SiC
| −74.4,<ref>{{cite journal |last1=Kleykamp |first1=H. |title=Gibbs Energy of Formation of SiC: A contribution to the Thermodynamic Stability of the Modifications |journal=Berichte der Bunsengesellschaft für physikalische Chemie |date=1998 |volume=102 |issue=9 |pages=1231–1234 |ref=SiC_a|doi=10.1002/bbpc.19981020928 }}</ref> −71.5<ref>{{cite web| url=https://janaf.nist.gov/tables/C-100.html |title= Silicon Carbide, Alpha (SiC) |author=<!--Not stated--> |date=March 1967 |access-date=5 February 2019|ref=SiC_b}}</ref>
|-
| [[Silicon tetrachloride]]
| Liquid
| SiCl<sub>4</sub>
| −640.1
|-
| [[Silica]] ([[Quartz]])
| Solid
| SiO<sub>2</sub>
| −910.86
|-
| [[Silver bromide]]
| Solid
| AgBr
| −99.5
|-
| [[Silver chloride]]
| Solid
| AgCl
| −127.01
|-
| [[Silver iodide]]
| Solid
| AgI
| −62.4
|-
| [[Silver oxide]]
| Solid
| Ag<sub>2</sub>O
| −31.1
|-
| [[Silver sulfide]]
| Solid
| Ag<sub>2</sub>S
| −31.8
|-
| [[Sodium]] || Solid
|| Na || 0
|-
| Sodium || Gas
|| Na || 107.5
|-
| [[Sodium bicarbonate]] || Solid
|| NaHCO<sub>3</sub> || −950.8
|-
| [[Sodium carbonate]]
| Solid
| Na<sub>2</sub>CO<sub>3</sub>
| −1130.77
|-
| [[Sodium chloride]]
| Aqueous
| NaCl
| −407.27
|-
| [[Sodium chloride]]
| Solid
| NaCl
| −411.12
|-
| [[Sodium chloride]]
| Liquid
| NaCl
| −385.92
|-
| [[Sodium chloride]]
| Gas
| NaCl
| −181.42
|-
|[[Sodium chlorate]]
|Solid
|NaClO<sub>3</sub>
| −365.4
|-
| [[Sodium fluoride]]
| Solid
| NaF
| −569.0
|-
| [[Sodium hydroxide]]
| Aqueous
| NaOH
| −469.15
|-
| [[Sodium hydroxide]]
| Solid
| NaOH
| −425.93
|-
|[[Sodium hypochlorite]]
|Solid
|NaOCl
|−347.1
|-
| [[Sodium nitrate]]
| Aqueous
| NaNO<sub>3</sub>
| −446.2
|-
| [[Sodium nitrate]]
| Solid
| NaNO<sub>3</sub>
| −424.8
|-
| [[Sodium oxide]]
| Solid
| Na<sub>2</sub>O
| −414.2
|-
| Sulfur (monoclinic) || Solid
|| S<sub>8</sub> || 0.3
|-
| Sulfur (rhombic) || Solid
|| S<sub>8</sub> || 0
|-
| [[Hydrogen sulfide]]
| Gas
| H<sub>2</sub>S
| −20.63
|-
| [[Sulfur dioxide]]
| Gas
| SO<sub>2</sub>
| −296.84
|-
| [[Sulfur trioxide]]
| Gas
| SO<sub>3</sub>
| −395.7
|-
| [[Sulfuric acid]]
| Liquid
| H<sub>2</sub>SO<sub>4</sub>
| −814
|-
| [[Titanium]]
| Gas
| Ti
| 468
|-
| [[Titanium tetrachloride]]
| Gas
| TiCl<sub>4</sub>
| −763.2
|-
| [[Titanium tetrachloride]]
| Liquid
| TiCl<sub>4</sub>
| −804.2
|-
| [[Titanium dioxide]]
| Solid
| TiO<sub>2</sub>
| −944.7
|-
| [[Zinc]]
| Gas
| Zn
| 130.7
|-
| [[Zinc chloride]]
| Solid
| ZnCl<sub>2</sub>
| −415.1
|-
| [[Zinc oxide]]
| Solid
| ZnO
| −348.0
|-
| [[Zinc sulfate]]|| Solid
|| ZnSO<sub>4</sub> || −980.14
|}

===Aliphatic hydrocarbons===
{| class="wikitable sortable sticky-header"
! Formula !! Name !! Δ<sub>f</sub>''H''<sup>⦵</sup> /(kcal/mol) !! Δ<sub>f</sub>''H''<sup>⦵</sup> /(kJ/mol)
|-
| colspan="4"| '''''Straight-chain'''''
|-
| CH<sub>4</sub> || [[Methane]] || −17.9 || −74.9
|-
| C<sub>2</sub>H<sub>6</sub> || [[Ethane]] || −20.0 || −83.7
|-
| C<sub>2</sub>H<sub>4</sub> || [[Ethylene]] || 12.5 || 52.5
|-
| C<sub>2</sub>H<sub>2</sub> || [[Acetylene]] || 54.2 || 226.8
|-
| C<sub>3</sub>H<sub>8</sub> || [[Propane]] || −25.0 || −104.6
|-
| C<sub>4</sub>H<sub>10</sub> || ''n''-[[Butane]] || −30.0 || −125.5
|-
| C<sub>5</sub>H<sub>12</sub> || ''n''-[[Pentane]] || −35.1 || −146.9
|-
| C<sub>6</sub>H<sub>14</sub> || ''n''-[[Hexane]] || −40.0 || −167.4
|-
| C<sub>7</sub>H<sub>16</sub> || ''n''-[[Heptane]] || −44.9 || −187.9
|-
| C<sub>8</sub>H<sub>18</sub> || ''n''-[[Octane]] || −49.8 || −208.4
|-
| C<sub>9</sub>H<sub>20</sub> || ''n''-[[Nonane]] || −54.8 || −229.3
|-
| C<sub>10</sub>H<sub>22</sub> || ''n''-[[Decane]] || −59.6 || −249.4
|-
| colspan="4"| '''''C<sub>4</sub> Alkane branched isomers'''''
|-
| C<sub>4</sub>H<sub>10</sub> || [[Isobutane]] (methylpropane) || −32.1 || −134.3
|-
| colspan="4"| '''''C<sub>5</sub> Alkane branched isomers'''''
|-
| C<sub>5</sub>H<sub>12</sub> || [[Neopentane]] (dimethylpropane) || −40.1 || −167.8
|-
| C<sub>5</sub>H<sub>12</sub> || [[Isopentane]] (methylbutane) || −36.9 || −154.4
|-
| colspan="4"| '''''C<sub>6</sub> Alkane branched isomers'''''
|-
| C<sub>6</sub>H<sub>14</sub> || [[2,2-Dimethylbutane]] || −44.5 || −186.2
|-
| C<sub>6</sub>H<sub>14</sub> || [[2,3-Dimethylbutane]] || −42.5 || −177.8
|-
| C<sub>6</sub>H<sub>14</sub> || [[2-Methylpentane]] (isohexane) || −41.8 || −174.9
|-
| C<sub>6</sub>H<sub>14</sub> || [[3-Methylpentane]] || −41.1 || −172.0
|-
| colspan="4"| '''''C<sub>7</sub> Alkane branched isomers'''''
|-
| C<sub>7</sub>H<sub>16</sub> || [[2,2-Dimethylpentane]] || −49.2 || −205.9
|-
| C<sub>7</sub>H<sub>16</sub> || [[2,2,3-Trimethylbutane]] || −49.0 || −205.0
|-
| C<sub>7</sub>H<sub>16</sub> || [[3,3-Dimethylpentane]] || −48.1 || −201.3
|-
| C<sub>7</sub>H<sub>16</sub> || [[2,3-Dimethylpentane]] || −47.3 || −197.9
|-
| C<sub>7</sub>H<sub>16</sub> || [[2,4-Dimethylpentane]] || −48.2 || −201.7
|-
| C<sub>7</sub>H<sub>16</sub> || [[2-Methylhexane]] || −46.5 || −194.6
|-
| C<sub>7</sub>H<sub>16</sub> || [[3-Methylhexane]] || −45.7 || −191.2
|-
| C<sub>7</sub>H<sub>16</sub> || [[3-Ethylpentane]] || −45.3 || −189.5
|-
| colspan="4"| '''''C<sub>8</sub> Alkane branched isomers'''''
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,3-Dimethylhexane]] || −55.1 || −230.5
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,2,3,3-Tetramethylbutane]] || −53.9 || −225.5
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,2-Dimethylhexane]] || −53.7 || −224.7
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,2,4-Trimethylpentane]] (isooctane) || −53.5 || −223.8
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,5-Dimethylhexane]] || −53.2 || −222.6
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,2,3-Trimethylpentane]] || −52.6 || −220.1
|-
| C<sub>8</sub>H<sub>18</sub> || [[3,3-Dimethylhexane]] || −52.6 || −220.1
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,4-Dimethylhexane]] || −52.4 || −219.2
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,3,4-Trimethylpentane]] || −51.9 || −217.1
|-
| C<sub>8</sub>H<sub>18</sub> || [[2,3,3-Trimethylpentane]] || −51.7 || −216.3
|-
| C<sub>8</sub>H<sub>18</sub> || [[2-Methylheptane]] || −51.5 || −215.5
|-
| C<sub>8</sub>H<sub>18</sub> || [[3-Ethyl-3-Methylpentane]] || −51.4 || −215.1
|-
| C<sub>8</sub>H<sub>18</sub> || [[3,4-Dimethylhexane]] || −50.9 || −213.0
|-
| C<sub>8</sub>H<sub>18</sub> || [[3-Ethyl-2-Methylpentane]] || −50.4 || −210.9
|-
| C<sub>8</sub>H<sub>18</sub> || [[3-Methylheptane]] || −60.3 || −252.5
|-
| C<sub>8</sub>H<sub>18</sub> || [[4-Methylheptane]] || ? || ?
|-
| C<sub>8</sub>H<sub>18</sub> || [[3-Ethylhexane]] || ? || ?
|-
| colspan="4"| '''''C<sub>9</sub> Alkane branched isomers (selected)'''''
|-
| C<sub>9</sub>H<sub>20</sub> || [[2,2,4,4-Tetramethylpentane]] || −57.8|| −241.8
|-
| C<sub>9</sub>H<sub>20</sub> || [[2,2,3,3-Tetramethylpentane]] || −56.7 || −237.2
|-
| C<sub>9</sub>H<sub>20</sub> || [[2,2,3,4-Tetramethylpentane]] || −56.6 || −236.8
|-
| C<sub>9</sub>H<sub>20</sub> || [[2,3,3,4-Tetramethylpentane]] || −56.4 || −236.0
|-
| C<sub>9</sub>H<sub>20</sub> || [[3,3-Diethylpentane]] || −55.7 || −233.0
|}

===Other organic compounds===

{| class="wikitable sortable sticky-header"
|-
! Species
! Phase
! Chemical formula
! Δ<sub>f</sub>''H''<sup>⦵</sup> /(kJ/mol)
|-
| [[Acetone]] || Liquid
|| C<sub>3</sub>H<sub>6</sub>O || −248.4
|-
| [[Benzene]]
| Liquid
| C<sub>6</sub>H<sub>6</sub>
| 48.95
|-
| [[Benzoic acid]]
| Solid
| C<sub>7</sub>H<sub>6</sub>O<sub>2</sub>
| −385.2
|-
| [[Carbon tetrachloride]]
| Liquid
| CCl<sub>4</sub>
| −135.4
|-
| [[Carbon tetrachloride]]
| Gas
| CCl<sub>4</sub>
| −95.98
|-
| [[Ethanol]]
| Liquid
| C<sub>2</sub>H<sub>5</sub>OH
| −277.0
|-
| [[Ethanol]]
| Gas
| C<sub>2</sub>H<sub>5</sub>OH
| −235.3
|-
| [[Glucose]]
| Solid
| C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>
| −1271
|-
| [[Isopropanol]] || Gas
|| C<sub>3</sub>H<sub>7</sub>OH || −318.1
|-
| [[Methanol]] (methyl alcohol)
| Liquid
| CH<sub>3</sub>OH
| −238.4
|-
| [[Methanol]] (methyl alcohol)
| Gas
| CH<sub>3</sub>OH
| −201.0
|-
| [[Methyl linoleate]] ([[Biodiesel]])
| Gas
| C<sub>19</sub>H<sub>34</sub>O<sub>2</sub>
| −356.3
|-
| [[Sucrose]] || Solid
|| C<sub>12</sub>H<sub>22</sub>O<sub>11</sub> || −2226.1
|-
| [[Trichloromethane]] ([[Chloroform]])
| Liquid
| CHCl<sub>3</sub>
| −134.47
|-
| [[Trichloromethane]] ([[Chloroform]])
| Gas
| CHCl<sub>3</sub>
| −103.18
|-
| [[Vinyl chloride]]
| Solid
| C<sub>2</sub>H<sub>3</sub>Cl
| −94.12
|}

== See also ==
* [[Calorimetry]]
* [[Thermochemistry]]

== References ==
{{reflist}}
* {{Cite book|last1=Zumdahl|first1= Steven |year=2009|title= Chemical Principles|edition= 6th |pages=384–387|publisher= Houghton Mifflin|location= Boston. New York|isbn= 978-0-547-19626-8}}

== External links ==
* [http://webbook.nist.gov/chemistry/ NIST Chemistry WebBook]

<!--Categories-->
[[Category:Enthalpy]]
[[Category:Thermochemistry]]

[[de:Enthalpie#Standardbildungsenthalpie]]