calcium oxide

Formula: CaO
Molecular weight: 56.077
IUPAC Standard InChI: InChI=1S/Ca.O
IUPAC Standard InChIKey: ODINCKMPIJJUCX-UHFFFAOYSA-N
CAS Registry Number: 1305-78-8
Chemical structure:
This structure is also available as a 2d Mol file
Other names: Calcium monoxide
Permanent link for this species. Use this link for bookmarking this species for future reference.
Information on this page:
Data at other public NIST sites:
Options:
- Switch to SI units

Gas phase thermochemistry data

Go To: Top, Condensed phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, References, Notes

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	10.50	kcal/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	52.512	cal/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973

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 (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Temperature (K)	4500. to 6000.
A	85.57620
B	-28.20000
C	3.986480
D	-0.198946
E	-147.0110
F	-170.5960
G	41.22770
H	10.50000
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Condensed phase thermochemistry data

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, References, Notes

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	-133.21	kcal/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{liquid,1 bar}	14.89	cal/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_solid	-151.75 ± 0.22	kcal/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_solid	-151.79	kcal/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{solid,1 bar}	9.11 ± 0.1	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
Quantity	Value	Units	Method	Reference	Comment
S°_solid	9.128	cal/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973

Liquid Phase Heat Capacity (Shomate Equation)

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Temperature (K)	3200. to 4500.
A	15.00000
B	1.106521×10^-7
C	-2.610032×10^-8
D	2.143000×10^-9
E	1.554651×10^-7
F	-141.4450
G	27.93760
H	-133.2060
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Solid Phase Heat Capacity (Shomate Equation)

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Temperature (K)	298. to 3200.
A	11.93930
B	1.168240
C	-0.084144
D	0.011039
E	-0.197203
F	-156.0640
G	22.12260
H	-151.7900
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Constants of diatomic molecules, References, Notes

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	6.66 ± 0.18	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	284.56	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	277.80	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
6.66 ± 0.18	END/DER	Dalleska and Armentrout, 1994	LL
6.5 ± 0.3	EVAL	Belyaev, Gotkis, et al., 1990	LL
7. ± 1.	EI	Farber, Srivastava, et al., 1987	LBLHLM
6.9 ± 0.15	DER	Murad, 1983	LBLHLM
7. ± 1.	EI	Farber and Srivastava, 1976	LLK
6.5	EI	Drowart, Exsteen, et al., 1964	RDSH

Constants of diatomic molecules

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, References, Notes

Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through September, 1976

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for ⁴⁰Ca¹⁶O
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
Progression of absorption bands (ΔG ~ 850) in Kr and Xe matrices, 20000 - 26000 cm^-1; observed for both Ca¹⁶O and Ca¹⁸O, but not definitely assigned.
↳Brewer and Wang, 1972
										(B → A')
↳Lejeune, 1945; Gaydon, 1955; missing citation; Volnyets, Kovalenok, et al., 1974
Orange system of strong emission bands, 15700 - 16700 cm^-1; no analysis.
↳Lejeune, 1945; Gaydon, 1955; missing citation; missing citation
C ¹Σ⁺	28857.8	560.9 Z	4.₀		0.3731 1	0.0032		(0.0000007)		1.989	C ↔ x 2 R	28772.4 Z
C ¹Σ⁺	↳missing citation; Veits and Gurvich, 1967
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
B ¹Π	25991	[574.4] Z			0.388₂ 3 1	0.005₅		(0.0000007)		1.950	B ↔ X 4 R	25913.0 Z
B ¹Π	↳Lagerqvist, 1954; Veits and Gurvich, 1967
A ¹Σ⁺	11554.8	718.9 Z	2.11		0.4059₂ 5	0.00137		5.4		1.9067	A → X R	11548.8₄ Z
A ¹Σ⁺	↳missing citation; missing citation; Brewer and Hauge, 1968; Field, 1974
A' ¹Π	8433	545.7 H	2.54		0.337	0.002₁				2.09₃	A' → X 6 R	8340
A' ¹Π	↳missing citation
a ³Π_i	(8313) 7	556	3.3		0.335					2.099
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
X ¹Σ⁺	0	732.1₁ Z	4.8₁ 8		0.4445₂			6.5₈ 9		1.8221	10

Notes

Perturbations.

ξ system of Lejeune and Rosen, 1945.

Value of B^Q; B^PR - B^Q = +0.0005.

η system of Lejeune and Rosen, 1945.

Many rotational perturbations by A' ¹Π and a ³Π_i Hultin and Lagerqvist, 1951, Field, 1974.

Directly observed for v' > 9 only; vibrational numbering determined from the perturbations in A ¹Σ⁺ Field, 1974.

A = -58, from perturbations in A ¹Σ⁺ as are the other constants for this state; see Field, 1974.

The vibrational constants in the Table are derived from levels with v ≤ 4 Hultin and Lagerqvist, 1951, Lagerqvist, 1954. From band heads in the A-X system (v" ≤ 13) and accounting for head-origin separations, Brewer and Hauge, 1968 have derived ω_e= 733.4 Brewer and Hauge, 1968, ω_ex_e= 5.28 Brewer and Hauge, 1968.

missing note

The question whether this is the ground state was for long in doubt but the observation by Ault and Andrews, 1975 of a fundamental frequency of 707 cm^-1 in a nitrogen matrix seems to settle it: see also Field, 1974 and the theoretical work of Carlson, Kaiser, et al., 1970. For computed ¹Σ ground state properties see Yoshimine, 1968.

From the Ca + ClO₂ chemiluminescence spectrum Engelke, Sander, et al., 1976. By contrast, the most recent mass-spectrometric Colin, Goldfinger, et al., 1964, Drowart, Exsteen, et al., 1964 and flame-photometric Kalff and Alkemade, 1973 determinations - corrected, where necessary, for a ¹Σ ground state - lead to D₀⁰ = 4.04 eV Kalff and Alkemade, 1973.

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, Notes

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Dalleska and Armentrout, 1994
Dalleska, N.F.; Armentrout, P.B., Guided ion beam studies of reactions of alkaline earth ions with O₂, Int. J. Mass Spectrom. Ion Processes, 1994, 134, 203. [all data]

Belyaev, Gotkis, et al., 1990
Belyaev, V.N.; Gotkis, I.S.; Lebedeva, N.L.; Krasnov, K.S., Ionization potentials of MX molecules (M = Ca, Sr, Ba; X = F, Cl, Br, I, OH, O), Russ. J. Phys. Chem., 1990, 64, 773. [all data]

Farber, Srivastava, et al., 1987
Farber, M.; Srivastava, R.D.; Moyer, J.W.; Leeper, J.D., Effusion mass spectrometric determination of thermodynamic properties of the gaseous mono- and di-hydroxides of calcium and KCaO(g), J. Chem. Soc. Faraday Trans. 2, 1987, 83, 3229. [all data]

Murad, 1983
Murad, E., Abstraction reactions of Ca⁺ and Sr⁺ ions, J. Chem. Phys., 1983, 78, 6611. [all data]

Farber and Srivastava, 1976
Farber, M.; Srivastava, R.D., The dissociation energies of calcium oxide and strontium oxide, High Temp. Sci., 1976, 8, 73. [all data]

Drowart, Exsteen, et al., 1964
Drowart, J.; Exsteen, G.; Verhaegen, G., Mass spectrometric determination of the dissociation energy of the molecules MgO, CaO, SrO and Sr₂O, J. Chem. Soc. Faraday Trans., 1964, 60, 1920. [all data]

Brewer and Wang, 1972
Brewer, L.; Wang, J.L.-F., Ground state of gaseous CaO; a study of the matrix spectra of Ca and CaO, J. Chem. Phys., 1972, 56, 4305. [all data]

Lejeune, 1945
Lejeune, J.-M., Application de la methode d'explosion de fils minces a l'etude du spectre de CaO, Bull. Soc. R. Sci. Liege, 1945, 14, 318. [all data]

Gaydon, 1955
Gaydon, A.G., Green and orange band spectra of CaOH, CaOD and calcium oxide, Proc. R. Soc. London A, 1955, 231, 437. [all data]

Volnyets, Kovalenok, et al., 1974
Volnyets, G.A.; Kovalenok, G.V.; Sokolov, V.A., Rotational structure of the 5472-5463 Å band of calcium oxide, Opt. Spectrosc. Engl. Transl., 1974, 36, 609, In original 1034. [all data]

Veits and Gurvich, 1967
Veits, I.V.; Gurvich, L.V., Investigation of the absorption spectra of molecules of difficulty volatile substances and radicals in shock waves, Dokl. Chem. Engl. Transl., 1967, 173, 377, In original 1325. [all data]

Lagerqvist, 1954
Lagerqvist, A., Ultra-violet and blue bands of calcium oxide, Ark. Fys., 1954, 8, 83. [all data]

Brewer and Hauge, 1968
Brewer, L.; Hauge, R., Near infrared bands of diatomic CaO and SrO, J. Mol. Spectrosc., 1968, 25, 330. [all data]

Field, 1974
Field, R.W., Assignment of the lowest ³Π and ¹Π states of CaO, SrO, and BaO, J. Chem. Phys., 1974, 60, 2400. [all data]

Lejeune and Rosen, 1945
Lejeune, J.-M.; Rosen, B., Contribution a l'etude du spectre de CaO, Bull. Soc. R. Sci. Liege, 1945, 14, 322. [all data]

Hultin and Lagerqvist, 1951
Hultin, M.; Lagerqvist, A., An infra-red band-system of calcium oxide, Ark. Fys., 1951, 2, 471. [all data]

Ault and Andrews, 1975
Ault, B.S.; Andrews, L., Nitrogen matrix reactions of alkaline earth metal atoms with ozone: infrared spectra of the alkaline earth metal oxide molecules, J. Chem. Phys., 1975, 62, 2320. [all data]

Carlson, Kaiser, et al., 1970
Carlson, K.D.; Kaiser, K.; Moser, C.; Wahl, A.C., Electronic structure and low-lying triplet states of CaO, J. Chem. Phys., 1970, 52, 4678. [all data]

Yoshimine, 1968
Yoshimine, Y., Computed ground state properties of BeO, MgO, CaO, and SrO in molecular orbital approximation, J. Phys. Soc. Jpn., 1968, 25, 1100. [all data]

Engelke, Sander, et al., 1976
Engelke, F.; Sander, R.K.; Zare, R.N., Crossed-beam chemiluminescent studies of alkaline earth atoms with ClO₂, J. Chem. Phys., 1976, 65, 1146. [all data]

Colin, Goldfinger, et al., 1964
Colin, R.; Goldfinger, P.; Jeunehomme, M., Mass-spectrometric studies of vaporization of the sulphides of calcium, strontium and barium. The dissociation energy of S₂ and SO, Trans. Faraday Soc., 1964, 60, 306. [all data]

Kalff and Alkemade, 1973
Kalff, P.J.; Alkemade, C.T.J., Determination of dissociation energies for some alkaline earth (hydro-) oxides in CO/N₂O flames, J. Chem. Phys., 1973, 59, 2572. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, References

Symbols used in this document:

IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
S°_{liquid,1 bar}	Entropy of liquid at standard conditions (1 bar)
S°_solid	Entropy of solid at standard conditions
S°_{solid,1 bar}	Entropy of solid at standard conditions (1 bar)
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fH°_liquid	Enthalpy of formation of liquid at standard conditions
Δ_fH°_solid	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. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
Customer support for NIST Standard Reference Data products.