Methane

• Formula: CH₄
• Molecular weight: 16.0425
• IUPAC Standard InChI:
  

  InChI=1S/CH4/h1H4 Download the identifier in a file.

• IUPAC Standard InChIKey: VNWKTOKETHGBQD-UHFFFAOYSA-N
• CAS Registry Number: 74-82-8
• Chemical structure:
  This structure is also available as a 2d Mol file or as a computed 3d SD file
  The 3d structure may be viewed using Java or Javascript.
• Other names: Marsh gas; Methyl hydride; CH4; Fire Damp; R 50; Biogas; R 50 (refrigerant)
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data (reactions 1 to 50)
  • IR Spectrum
  • Mass spectrum (electron ionization)
  • Vibrational and/or electronic energy levels
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 51 to 100, reactions 101 to 112
  • Henry's Law data
  • Gas phase ion energetics data
  • Ion clustering data
  • Fluid Properties
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Computational Chemistry Comparison and Benchmark Database
  • Gas Phase Kinetics Database
• Options:
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Gas phase thermochemistry data

Go To: Top, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
DRB - Donald R. Burgess, Jr.
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
fH°gas	-74.87	kJ/mol	Review	Chase, 1998	Data last reviewed in March, 1961
fH°gas	-74.6 ± 0.3	kJ/mol	Review	Manion, 2002	adopted recommendation of Gurvich, Veyts, et al., 1991; DRB
fH°gas	-74.5 ± 0.4	kJ/mol	Ccb	Pittam and Pilcher, 1972	ALS
fH°gas	-74.85 ± 0.31	kJ/mol	Ccb	Prosen and Rossini, 1945	Hf derived from Heat of Hydrogenation; ALS
fH°gas	-73.4 ± 1.1	kJ/mol	Ccb	Roth and Banse, 1932	Reanalyzed by Cox and Pilcher, 1970, Original value = -75.19 kJ/mol; ALS
Quantity	Value	Units	Method	Reference	Comment
cH°gas	-890.7 ± 0.4	kJ/mol	Ccb	Pittam and Pilcher, 1972	Corresponding «DELTA»fHºgas = -74.48 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
cH°gas	-890.35 ± 0.30	kJ/mol	Ccb	Prosen and Rossini, 1945	Hf derived from Heat of Hydrogenation; Corresponding «DELTA»fHºgas = -74.822 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
cH°gas	-891.8 ± 1.1	kJ/mol	Ccb	Roth and Banse, 1932	Reanalyzed by Cox and Pilcher, 1970, Original value = -887.3 ± 1.0 kJ/mol; Corresponding «DELTA»fHºgas = -73.39 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
cH°gas	-890.16 ± 0.30	kJ/mol	Cm	Rossini, 1931	Corresponding «DELTA»fHºgas = -75.010 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°gas	188.66 ± 0.42	J/mol*K	N/A	Colwell J.H., 1963	The calorimetric value is significantly higher than the statistically calculated entropy, 186.26 J/mol*K, which remains the best value for use in thermodynamic calculations [ Vogt G.J., 1976, Friend D.G., 1989, Gurvich, Veyts, et al., 1989]. Earlier the value of 185.3 J/mol*K was calculated from experimental data [ Giauque W.F., 1931]. The value of S(298.15 K)=185.94 J/mol*K was obtained by high accuracy ab initio calculation [ East A.L.L., 1997].; GT
Quantity	Value	Units	Method	Reference	Comment
S°gas,1 bar	186.25	J/mol*K	Review	Chase, 1998	Data last reviewed in March, 1961

Constant pressure heat capacity of gas

Constant pressure heat capacity of gas

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
    C_p = heat capacity (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/mol*K)
    t = temperature (K) / 1000.

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Phase change data

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Kenneth Kroenlein director
DH - Eugene S. Domalski and Elizabeth D. Hearing
AC - William E. Acree, Jr., James S. Chickos

Quantity	Value	Units	Method	Reference	Comment
Tboil	111. ± 2.	K	AVG	N/A	Average of 13 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Tfus	85.7	K	N/A	Streng, 1971	Uncertainty assigned by TRC = 0.2 K; TRC
Tfus	90.6	K	N/A	Van't Zelfde, Omar, et al., 1968	Uncertainty assigned by TRC = 0.3 K; TRC
Tfus	91.2	K	N/A	Timmermans, 1935	Uncertainty assigned by TRC = 2. K; TRC
Tfus	90.6	K	N/A	Clusius, 1929	Uncertainty assigned by TRC = 0.2 K; TRC
Tfus	90.5	K	N/A	Eucken and Karwat, 1924	Uncertainty assigned by TRC = 0.2 K; TRC
Quantity	Value	Units	Method	Reference	Comment
Ttriple	90.67 ± 0.03	K	AVG	N/A	Average of 25 out of 32 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Ptriple	0.1169 ± 0.0006	bar	AVG	N/A	Average of 20 out of 23 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Tc	190.6 ± 0.3	K	AVG	N/A	Average of 19 out of 23 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Pc	46.1 ± 0.3	bar	AVG	N/A	Average of 16 out of 21 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Vc	0.09860	l/mol	N/A	Ambrose and Tsonopoulos, 1995
Vc	0.09852	l/mol	N/A	Younglove and Ely, 1987	TRC
Vc	0.100	l/mol	N/A	Terry, Lynch, et al., 1969	Uncertainty assigned by TRC = 0.001 l/mol; TRC
Quantity	Value	Units	Method	Reference	Comment
c	10.1 ± 0.2	mol/l	AVG	N/A	Average of 16 out of 17 values; Individual data points

Enthalpy of vaporization

vapH (kJ/mol)	Temperature (K)	Method	Reference	Comment
8.519	99.54	N/A	Vogt and Pitzer, 1976	P = 2.81 kPa Data from Frank and Clusius, 1937 and 39FRA/CLU.; DH
8.6	101.	N/A	Stock, Henning, et al., 2006	Based on data from 92. - 110. K. See also Boublik, Fried, et al., 1984.; AC
8.6	105.	A	Stephenson and Malanowski, 1987	Based on data from 90. - 120. K.; AC
8.4	134.	A	Stephenson and Malanowski, 1987	Based on data from 115. - 149. K.; AC
8.7	174.	A	Stephenson and Malanowski, 1987	Based on data from 148. - 189. K.; AC
8.17	111.7	N/A	Majer and Svoboda, 1985
8.6	112.	N/A	Ott, Goates, et al., 1972	Based on data from 91. - 127. K. See also Boublik, Fried, et al., 1984.; AC
8.5	175.	N/A	Ott, Goates, et al., 1972	Based on data from 91. - 190. K.; AC
8.1	137.	N/A	Reid, 1972	AC
8.6	175.	N/A	Ambrose, Counsell, et al., 1970	Based on data from 100. - 190. K.; AC
8.2	112.	C	Hestermans and White, 1961	AC
7.5	130.	C	Hestermans and White, 1961	AC
5.9	160.	C	Hestermans and White, 1961	AC
4.0	180.	C	Hestermans and White, 1961	AC
8.5	149.	N/A	Hestermans and White, 1961	Based on data from 109. - 189. K.; AC
8.5 ± 0.1	99.	N/A	Frank and Clusius, 1939	AC

Enthalpy of vaporization

Δ_vapH = A exp(-αT_r) (1 − T_r)^β
    Δ_vapH = Enthalpy of vaporization (at saturation pressure) (kJ/mol)
    T_r = reduced temperature (T / T_c)

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Temperature (K)	112. - 180.
A (kJ/mol)	10.11
	-0.22
	0.388
Tc (K)	190.6
Reference	Majer and Svoboda, 1985

Entropy of vaporization

vapS (J/mol*K)	Temperature (K)	Reference	Comment
85.58	99.54	Vogt and Pitzer, 1976	P; DH

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (bar)
    T = temperature (K)

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Enthalpy of sublimation

subH (kJ/mol)	Temperature (K)	Method	Reference	Comment
9.7	72.	N/A	Stephenson and Malanowski, 1987	Based on data from 53. - 91. K.; AC
9.2	72.	N/A	Bondi, 1963	Based on data from 54. - 90. K. See also Armstrong, Brickwedde, et al., 1955.; AC
10.0	84.	N/A	Jones, 1960	Based on data from 79. - 89. K.; AC
9.7	63.	A,MS	Tickner and Lossing, 1951	Based on data from 48. - 78. K.; AC
9.62	77.	A	Stull, 1947	Based on data from 67. - 88. K.; AC

Enthalpy of phase transition

Htrs (kJ/mol)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
0.09355	20.53	crystaline, II	crystaline, I	Vogt and Pitzer, 1976	Lambda transition.; DH
0.9392	90.67	crystaline, I	liquid	Vogt and Pitzer, 1976	DH

Entropy of phase transition

Strs (J/mol*K)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
4.557	20.53	crystaline, II	crystaline, I	Vogt and Pitzer, 1976	Lambda; DH
10.36	90.67	crystaline, I	liquid	Vogt and Pitzer, 1976	DH

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, Phase change data, IR Spectrum, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
B - John E. Bartmess
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
MS - José A. Martinho Simões
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Reactions 1 to 50

CH₃^- +  =

By formula: CH₃^- + H⁺ = CH₄

Quantity	Value	Units	Method	Reference	Comment
rH°	1743.6 ± 2.9	kJ/mol	D-EA	Ellison, Engelking, et al., 1978	gas phase; B
rH°	1749. ± 15.	kJ/mol	CIDT	Graul and Squires, 1990	gas phase; B
rH°	>1691.1 ± 0.42	kJ/mol	G+TS	Bohme, Lee-Ruff, et al., 1972	gas phase; B
rH°	1735.5	kJ/mol	N/A	Check, Faust, et al., 2001	gas phase; FeBr3; ; «DELTA»S(EA)=9.3; B
Quantity	Value	Units	Method	Reference	Comment
rG°	1709.8 ± 3.3	kJ/mol	H-TS	Ellison, Engelking, et al., 1978	gas phase; B
rG°	1715. ± 15.	kJ/mol	H-TS	Graul and Squires, 1990	gas phase; B
rG°	>1657.3	kJ/mol	IMRB	Bohme, Lee-Ruff, et al., 1972	gas phase; B
rG°	1704.1	kJ/mol	N/A	Check, Faust, et al., 2001	gas phase; FeBr3; ; «DELTA»S(EA)=9.3; B

(CH₅⁺  ) +  = (CH₅⁺  2)

By formula: (CH₅⁺  CH₄) + CH₄ = (CH₅⁺  2CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	22. ± 1.	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rH°	25.	kJ/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
rH°	6.3	kJ/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
rS°	104.	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rS°	102.	J/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
rS°	30.	J/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

CH₅⁺ +  = (CH₅⁺  )

By formula: CH₅⁺ + CH₄ = (CH₅⁺  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	29. ± 1.	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rH°	31.	kJ/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
rH°	17.	kJ/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
rS°	92.5	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rS°	87.0	J/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
rS°	51.9	J/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

C₂H₅⁺ +  = (C₂H₅⁺  )

By formula: C₂H₅⁺ + CH₄ = (C₂H₅⁺  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	23.0	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
rH°	28.	kJ/mol	PHPMS	Hiroka and Kebarle, 1975	gas phase; M
rH°	10.	kJ/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
rS°	92.9	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
rS°	97.9	J/mol*K	PHPMS	Hiroka and Kebarle, 1975	gas phase; M
rS°	36.	J/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

(  2) +  = (  3)

By formula: (Co⁺  2CH₄) + CH₄ = (Co⁺  3CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	46.	kJ/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	84.	J/mol*K	N/A	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
41. (+5.0,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

Free energy of reaction

rG° (kJ/mol)	T (K)	Method	Reference	Comment
3.	477.	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M

 +  = (  )

By formula: Co⁺ + CH₄ = (Co⁺  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rS°	82.8	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(530 K); M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
90.0 (+6.7,-0.)		CID	Haynes and Armentrout, 1996	gas phase; guided ion beam CID; M
90.0 (+5.9,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M
94. (+2.,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(530 K); M

(  ) +  = (    )

By formula: (Co⁺  CH₄) + H₂ = (Co⁺  H₂  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rS°	95.8	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+).2H2, «DELTA»rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
73. (+3.,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+).2H2, «DELTA»rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

(  ) +  = (    )

By formula: (Co⁺  H₂) + CH₄ = (Co⁺  CH₄  H₂)

Quantity	Value	Units	Method	Reference	Comment
rS°	91.2	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+)2H2, «DELTA»rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
94.6 (+5.0,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+)2H2, «DELTA»rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

 (g) = C₅MnO₅ (g) +  (g)

By formula: C₆H₃MnO₅ (g) = C₅MnO₅ (g) + CH₄ (g)

Quantity	Value	Units	Method	Reference	Comment
rH°	192. ± 15.	kJ/mol	PIMS	Martinho Simões and Beauchamp, 1990	The reaction enthalpy was derived from the appearance energy of Mn(CO)5(+), 940.7 ± 4.8 kJ/mol, using Mn(CO)5(Me) as the neutral precursor, together with the adiabatic ionization energy of Mn(CO)5 radical, 749. ± 14. kJ/mol Martinho Simões and Beauchamp, 1990; MS

(  ) +  = (  2)

By formula: (Co⁺  CH₄) + CH₄ = (Co⁺  2CH₄)

Quantity	Value	Units	Method	Reference	Comment
rS°	109.	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(500 K); M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
95.8 (+5.0,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M
104. (+4.2,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(500 K); M

(CH₅⁺  2) +  = (CH₅⁺  3)

By formula: (CH₅⁺  2CH₄) + CH₄ = (CH₅⁺  3CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	13.1 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rH°	17.	kJ/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	93.7	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rS°	109.	J/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

(CH₅⁺  3) +  = (CH₅⁺  4)

By formula: (CH₅⁺  3CH₄) + CH₄ = (CH₅⁺  4CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	12.6 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rH°	16.	kJ/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	99.2	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
rS°	111.	J/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

 (g) + CH₃BrMg (solution) =  (solution) + Br₂Mg (solution)

By formula: HBr (g) + CH₃BrMg (solution) = CH₄ (solution) + Br₂Mg (solution)

Quantity	Value	Units	Method	Reference	Comment
rH°	-274.5 ± 2.2	kJ/mol	RSC	Holm, 1981	solvent: Diethyl ether; The enthalpy of formation was calculated using the assumptions and the auxiliary data in Holm, 1981, except for the organic compound, whose enthalpy of formation was quoted from Pedley, 1994; MS

(  ) +  = (    )

By formula: (Co⁺  CH₄) + C₂H₆ = (Co⁺  C₂H₆  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rS°	108.	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+).2CH4, «DELTA»rS(480 K); M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
119. (+5.4,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+).2CH4, «DELTA»rS(480 K); M

C₆₃H₉₁CoN₁₃O₁₄P (solution) =  (solution) +  (solution)

By formula: C₆₃H₉₁CoN₁₃O₁₄P (solution) = C₆₃H₈₈CoN₁₄O₁₄P (solution) + CH₄ (solution)

Quantity	Value	Units	Method	Reference	Comment
rH°	155. ± 13.	kJ/mol	KinS	Martin and Finke, 1990	solvent: Ethylene glycol; Please also see Martin and Finke, 1992. The reaction enthalpy relies on 172. ± 13. kJ/mol for the reaction activation enthalpy. The reaction refers to "base-on" cobalamine.; MS

C₃H₇⁺ +  = (C₃H₇⁺  )

By formula: C₃H₇⁺ + CH₄ = (C₃H₇⁺  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	10.8	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
rH°	14.	kJ/mol	PHPMS	Hiraoka and Kebarle, 1976	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	72.8	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
rS°	84.	J/mol*K	PHPMS	Hiraoka and Kebarle, 1976	gas phase; M

 +  =  + 

By formula: HI + CH₃I = CH₄ + I₂

Quantity	Value	Units	Method	Reference	Comment
rH°	-52.55 ± 0.54	kJ/mol	Eqk	Golden, Walsh, et al., 1965	gas phase; ALS
rH°	-53.0 ± 0.2	kJ/mol	Eqk	Goy and Pritchard, 1965	gas phase; ALS
rH°	-46.2 ± 5.6	kJ/mol	Cm	Nichol and Ubbelohde, 1952	gas phase; ALS

(C₂H₅⁺  9) +  = (C₂H₅⁺  10)

By formula: (C₂H₅⁺  9CH₄) + CH₄ = (C₂H₅⁺  10CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	7.99	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	92.	J/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

(C₃H₇⁺  7) +  = (C₃H₇⁺  8)

By formula: (C₃H₇⁺  7CH₄) + CH₄ = (C₃H₇⁺  8CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.28	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	92.	J/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

(C₄H₉⁺  8) +  = (C₄H₉⁺  9)

By formula: (C₄H₉⁺  8CH₄) + CH₄ = (C₄H₉⁺  9CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	7.78	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	84.	J/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

(CH₅⁺  8) +  = (CH₅⁺  9)

By formula: (CH₅⁺  8CH₄) + CH₄ = (CH₅⁺  9CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	6.44	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
rS°	84.	J/mol*K	N/A	Hiraoka and Mori, 1989	gas phase; Entropy change calculated or estimated; M

(  ) +  = (    )

By formula: (Co⁺  H₂O) + CH₄ = (Co⁺  CH₄  H₂O)

Quantity	Value	Units	Method	Reference	Comment
rS°	113.	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(525 K); M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
108. (+3.,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(525 K); M

(  ) +  = (  2)

By formula: (H₃O⁺  CH₄) + CH₄ = (H₃O⁺  2CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	14.	kJ/mol	HPMS	Bennet and Field, 1972	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
rS°	34.	J/mol*K	HPMS	Bennet and Field, 1972	gas phase; Entropy change is questionable; M

(  ) +  = (    )

By formula: (Co⁺  C₂H₆) + CH₄ = (Co⁺  CH₄  C₂H₆)

Quantity	Value	Units	Method	Reference	Comment
rS°	110.	J/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(490 K); M

Enthalpy of reaction

rH° (kJ/mol)	T (K)	Method	Reference	Comment
102. (+4.6,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; «DELTA»rS(490 K); M

 +  = (  )

By formula: H₄N⁺ + CH₄ = (H₄N⁺  CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	15.	kJ/mol	HPMS	Bennet and Field, 1972, 2	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
rS°	64.9	J/mol*K	HPMS	Bennet and Field, 1972, 2	gas phase; Entropy change is questionable; M

 (g) +  (cr) =  (g) +  (cr)

By formula: HBr (g) + CH₃Li (cr) = CH₄ (g) + BrLi (cr)

Quantity	Value	Units	Method	Reference	Comment
rH°	-317.3 ± 2.0	kJ/mol	RSC	Holm, 1974	Please also see Pedley and Rylance, 1977. The reaction enthalpy was quoted from Pedley and Rylance, 1977. See Liebman, Martinho Simões, et al., 1995 for comments; MS

2 +  =  + 2

By formula: 2H₂ + CH₂Cl₂ = CH₄ + 2HCl

Quantity	Value	Units	Method	Reference	Comment
rH°	-163.4 ± 1.3	kJ/mol	Chyd	Lacher, Amador, et al., 1967	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -167.7 ± 1.3 kJ/mol; At 250 C; ALS

 (l) + (  100) (solution) = 2 (g) + (  100) (solution)

By formula: C₂H₆Zn (l) + (H₂O₄S  100H₂O) (solution) = 2CH₄ (g) + (O₄SZn  100H₂O) (solution)

Quantity	Value	Units	Method	Reference	Comment
rH°	-341.8 ± 0.8	kJ/mol	RSC	Carson, Hartley, et al., 1949	Please also see Pedley and Rylance, 1977 and Cox and Pilcher, 1970, 2.; MS

(CH₅⁺  4) +  = (CH₅⁺  5)

By formula: (CH₅⁺  4CH₄) + CH₄ = (CH₅⁺  5CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	11.7 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	104.	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺  5) +  = (CH₅⁺  6)

By formula: (CH₅⁺  5CH₄) + CH₄ = (CH₅⁺  6CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	11.3 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	106.	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺  6) +  = (CH₅⁺  7)

By formula: (CH₅⁺  6CH₄) + CH₄ = (CH₅⁺  7CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	11.2 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	111.	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺  7) +  = (CH₅⁺  8)

By formula: (CH₅⁺  7CH₄) + CH₄ = (CH₅⁺  8CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.5 ± 0.8	kJ/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	90.4	J/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(C₂H₅⁺  2) +  = (C₂H₅⁺  3)

By formula: (C₂H₅⁺  2CH₄) + CH₄ = (C₂H₅⁺  3CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.54	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	74.9	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  3) +  = (C₂H₅⁺  4)

By formula: (C₂H₅⁺  3CH₄) + CH₄ = (C₂H₅⁺  4CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.46	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	77.0	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  4) +  = (C₂H₅⁺  5)

By formula: (C₂H₅⁺  4CH₄) + CH₄ = (C₂H₅⁺  5CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.29	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	79.1	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  5) +  = (C₂H₅⁺  6)

By formula: (C₂H₅⁺  5CH₄) + CH₄ = (C₂H₅⁺  6CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.25	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	81.2	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  6) +  = (C₂H₅⁺  7)

By formula: (C₂H₅⁺  6CH₄) + CH₄ = (C₂H₅⁺  7CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.91	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	86.6	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  7) +  = (C₂H₅⁺  8)

By formula: (C₂H₅⁺  7CH₄) + CH₄ = (C₂H₅⁺  8CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.79	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	87.9	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺  8) +  = (C₂H₅⁺  9)

By formula: (C₂H₅⁺  8CH₄) + CH₄ = (C₂H₅⁺  9CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.70	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	91.2	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺  2) +  = (C₃H₇⁺  3)

By formula: (C₃H₇⁺  2CH₄) + CH₄ = (C₃H₇⁺  3CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.46	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	77.0	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺  3) +  = (C₃H₇⁺  4)

By formula: (C₃H₇⁺  3CH₄) + CH₄ = (C₃H₇⁺  4CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.20	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	79.5	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺  4) +  = (C₃H₇⁺  5)

By formula: (C₃H₇⁺  4CH₄) + CH₄ = (C₃H₇⁺  5CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.20	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	87.4	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺  5) +  = (C₃H₇⁺  6)

By formula: (C₃H₇⁺  5CH₄) + CH₄ = (C₃H₇⁺  6CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.16	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	87.9	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺  6) +  = (C₃H₇⁺  7)

By formula: (C₃H₇⁺  6CH₄) + CH₄ = (C₃H₇⁺  7CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.04	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	91.2	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  2) +  = (C₄H₉⁺  3)

By formula: (C₄H₉⁺  2CH₄) + CH₄ = (C₄H₉⁺  3CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.92	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	82.4	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  3) +  = (C₄H₉⁺  4)

By formula: (C₄H₉⁺  3CH₄) + CH₄ = (C₄H₉⁺  4CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.87	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	83.7	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  4) +  = (C₄H₉⁺  5)

By formula: (C₄H₉⁺  4CH₄) + CH₄ = (C₄H₉⁺  5CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	9.25	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	81.2	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  5) +  = (C₄H₉⁺  6)

By formula: (C₄H₉⁺  5CH₄) + CH₄ = (C₄H₉⁺  6CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.74	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	80.8	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  6) +  = (C₄H₉⁺  7)

By formula: (C₄H₉⁺  6CH₄) + CH₄ = (C₄H₉⁺  7CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.58	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	82.4	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺  7) +  = (C₄H₉⁺  8)

By formula: (C₄H₉⁺  7CH₄) + CH₄ = (C₄H₉⁺  8CH₄)

Quantity	Value	Units	Method	Reference	Comment
rH°	8.33	kJ/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
rS°	84.1	J/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

IR Spectrum

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, References, Notes

Data compiled by: Coblentz Society, Inc.

• GAS (150 mmHg DILUTED TO A TOTAL PRESSURE OF 600 mmHg WITH N2); DOW KBr FOREPRISM; DIGITIZED BY NIST FROM HARD COPY (FROM TWO SEGMENTS); 4 cm^-1 resolution

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

• gas

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Vibrational and/or electronic energy levels, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

Vibrational and/or electronic energy levels

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: Takehiko Shimanouchi

Symmetry:   T_d     Symmetry Number = 12

Source: Shimanouchi, 1972

Notes

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Chase, 1998
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Pittam and Pilcher, 1972
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Colwell J.H., 1963
Colwell J.H., Thermodynamic properties of CH4 and CD4. Interpretation of the properties of solid, J. Chem. Phys., 1963, 39, 635-653. [all data]

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Gurvich, L.V.; Veyts, I.V.; Alcock, C.B., Thermodynamic Properties of Individual Substances, 4th ed.; Vols. 1 and 2, Hemisphere, New York, 1989. [all data]

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East A.L.L., Ab initio statistical thermodynamical models for the computation of third-law entropies, J. Chem. Phys., 1997, 106, 6655-6674. [all data]

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Halford J.O., Standard heat capacities of gaseous methanol, ethanol, methane and ethane at 279 K by thermal conductivity, J. Phys. Chem., 1957, 61, 1536-1539. [all data]

McDowell R.S., 1963
McDowell R.S., Thermodynamic functions of methane, J. Chem. Eng. Data, 1963, 8, 547-548. [all data]

Streng, 1971
Streng, A.G., Miscibility and Compatibility of Some Liquid and Solidified Gases at Low Temperature, J. Chem. Eng. Data, 1971, 16, 357. [all data]

Van't Zelfde, Omar, et al., 1968
Van't Zelfde, P.; Omar, M.H.; LePair-Schroten, H.G.M.; Dokoupil, Z., Solid-liquid equilibrium diagram for the argon + methane system., Physica (Amsterdam), 1968, 38, 241-51. [all data]

Timmermans, 1935
Timmermans, J., Researches in Stoichiometry. I. The Heat of Fusion of Organic Compounds., Bull. Soc. Chim. Belg., 1935, 44, 17-40. [all data]

Clusius, 1929
Clusius, K., The specific heat of several condensed gases between 10deg. abs. and their triple point., Z. Phys. Chem., Abt. B, 1929, 3, 41. [all data]

Eucken and Karwat, 1924
Eucken, A.; Karwat, E., Determination of the heat content of several condensed gases, Z. Phys. Chem., Stoechiom. Verwandtschaftsl., 1924, 112, 467. [all data]

Ambrose and Tsonopoulos, 1995
Ambrose, D.; Tsonopoulos, C., Vapor-Liquid Critical Properties of Elements and Compounds. 2. Normal Alkenes, J. Chem. Eng. Data, 1995, 40, 531-546. [all data]

Younglove and Ely, 1987
Younglove, B.A.; Ely, J.F., Thermophysical Properties of Fluids II. Methane, Ethane, Propane, Isobutane, and Normal Butane, J. Phys. Chem. Ref. Data, 1987, 16, 577. [all data]

Terry, Lynch, et al., 1969
Terry, M.J.; Lynch, J.T.; Bunclark, M.; Mansell, K.R.; Staveley, L.A.K., The Densities of Liquid Argon, Krypton, Xenon, Oxygen, Nitrogen, Carbon Monoxide, Methane and Carbon Tetrafluoride Along the Orthobaric Liquid Curve, J. Chem. Thermodyn., 1969, 1, 413. [all data]

Vogt and Pitzer, 1976
Vogt, G.J.; Pitzer, K.S., Entropy and heat capacity of methane, spin-species conversion, J. Chem. Thermodynam., 1976, 8, 1011-1031. [all data]

Frank and Clusius, 1937
Frank, A.; Clusius, K., The entropy of methane, Z. Physik. Chem., 1937, B36, 291-300. [all data]

Stock, Henning, et al., 2006
Stock, Alfred; Henning, Fritz; Kuß, Ernst, Dampfdrucktafeln für Temperaturbestimmungen zwischen + 25° und - 185°, Ber. dtsch. Chem. Ges. A/B, 2006, 54, 5, 1119-1129, https://doi.org/10.1002/cber.19210540531 . [all data]

Boublik, Fried, et al., 1984
Boublik, T.; Fried, V.; Hala, E., The Vapour Pressures of Pure Substances: Selected Values of the Temperature Dependence of the Vapour Pressures of Some Pure Substances in the Normal and Low Pressure Region, 2nd ed., Elsevier, New York, 1984, 972. [all data]

Stephenson and Malanowski, 1987
Stephenson, Richard M.; Malanowski, Stanislaw, Handbook of the Thermodynamics of Organic Compounds, 1987, https://doi.org/10.1007/978-94-009-3173-2 . [all data]

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Majer, V.; Svoboda, V., Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation, Blackwell Scientific Publications, Oxford, 1985, 300. [all data]

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Ott, J. Bevan; Goates, J. Rex; Lamb, John D., Solid-liquid phase equilibria in water + ethylene glycol, The Journal of Chemical Thermodynamics, 1972, 4, 1, 123-126, https://doi.org/10.1016/S0021-9614(72)80015-6 . [all data]

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Reid, Robert C., Handbook on vapor pressure and heats of vaporization of hydrocarbons and related compounds, R. C. Wilhort and B. J. Zwolinski, Texas A Research Foundation. College Station, Texas(1971). 329 pages.$10.00, AIChE J., 1972, 18, 6, 1278-1278, https://doi.org/10.1002/aic.690180637 . [all data]

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Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), Vibrational and/or electronic energy levels, References

• Symbols used in this document:
  

  Cp,gas	Constant pressure heat capacity of gas
  Pc	Critical pressure
  Ptriple	Triple point pressure
  S°gas	Entropy of gas at standard conditions
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  T	Temperature
  Tboil	Boiling point
  Tc	Critical temperature
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  Vc	Critical volume
  Htrs	Enthalpy of phase transition
  Strs	Entropy of phase transition
  cH°gas	Enthalpy of combustion of gas at standard conditions
  fH°gas	Enthalpy of formation of gas at standard conditions
  rG°	Free energy of reaction at standard conditions
  rH°	Enthalpy of reaction at standard conditions
  rS°	Entropy of reaction at standard conditions
  subH	Enthalpy of sublimation
  vapH	Enthalpy of vaporization
  vapS	Entropy of vaporization
  c	Critical density

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