Ammonia (data page)

This page provides supplementary chemical data on ammonia.

Structure and properties

Molecular structure
Point group	C_3v
Bond length	101.2 pm (N–H)^[1]
Bond angle	106.7° (H–N–H)^[1]
Bond strength	435 kJ/mol (H–NH₂)
Crystal data
Crystal structure	?
Properties
Dipole moment	1.46 D
Dielectric constant	22 ε₀ at 239 K
Magnetic susceptibility	diamagnetic
Acidity of NH₄⁺ (pK_a)	9.25

Thermodynamic properties

Phase diagram and crystalline states of ammonia
I. cubic, II. hcp, III. fcc, IV. orthrombic

Phase behavior
Triple point	195.4 K (–77.75 °C), 6.060 kPa
Critical point	405.5 K (132.3 °C), 11.300 MPa
Std enthalpy change of fusion, Δ_fusH^o	+5.653 kJ/mol
Std entropy change of fusion, Δ_fusS^o	+28.93 J/(mol·K)
Std enthalpy change of vaporization, Δ_vapH^o	+23.35 kJ/mol at BP of –33.4 °C
Std entropy change of vaporization, Δ_vapS^o	+97.41 J/(mol·K) at BP of –33.4 °C
Solid properties
Std enthalpy change of formation, Δ_fH^o_solid	? kJ/mol
Standard molar entropy, S^o_solid	? J/(mol K)
Heat capacity, c_p	? J/(mol K)
Liquid properties
Std enthalpy change of formation, Δ_fH^o_liquid	? kJ/mol
Standard molar entropy, S^o_liquid	? J/(mol K)
Heat capacity, c_p	80.80 J/(mol K)
Gas properties
Std enthalpy change of formation, Δ_fH^o_gas	−45.92 kJ/mol
Std Gibbs free energy change of formation, Δ_fG^o_gas	−16.6 kJ/mol
Standard molar entropy, S^o_gas	192.77 J/(mol K)
Heat capacity, c_p	35.06 J/(mol K)
Heat capacity ratio, γ at 15 °C	1.310
van der Waals' constants	a = 422.5 liter² kPa / mole² b = 0.03707 liter / mole

Vapor–liquid equilibrium data

P in mm Hg		1	10	40	100	400	760	1520	3800	7600	15600	30400	45600
T in °C		–109.1_(s)	–91.9_(s)	–79.2_(s)	–68.4	–45.4	–33.6	–18.7	4.7	25.7	50.1	78.9	98.3

Table data (above) obtained from CRC Handbook of Chemistry and Physics 44th ed. The (s) notation indicates equilibrium temperature of vapor over solid. Otherwise temperature is equilibrium of vapor over liquid.

log₁₀ of anydrous ammonia vapor pressure. Uses formula shown below.

Vapor pressure formula for ammonia:^[2]

log₁₀(P) = A – B / (T – C)

where P is pressure in kPa and T is temperature in Kelvin

A = 6.67956; B = 1002.711; C = 25.215 for T = 190 K through 333 K

Vapor over Anhydrous Ammonia^[3]
Temp.	Pressure	ρ of liquid	ρ of vapor	Δ_vapH
–78 °C	5.90 kPa
–75 °C	7.93 kPa	0.73094 g/cm³	7.8241×10⁻⁵ g/cm³
–70 °C	10.92 kPa	0.72527 g/cm³	1.1141×10⁻⁴ g/cm³
–65 °C	15.61 kPa	0.71953 g/cm³	1.5552×10⁻⁴ g/cm³
–60 °C	21.90 kPa	0.71378 g/cm³	2.1321×10⁻⁴ g/cm³
–55 °C	30.16 kPa	0.70791 g/cm³	2.8596×10⁻⁴ g/cm³
–50 °C	40.87 kPa	0.70200 g/cm³	3.8158×10⁻⁴ g/cm³	1417 J/g
–45 °C	54.54 kPa	0.69604 g/cm³	4.9940×10⁻⁴ g/cm³	1404 J/g
–40 °C	71.77 kPa	0.68999 g/cm³	6.4508×10⁻⁴ g/cm³	1390 J/g
–35 °C	93.19 kPa	0.68385 g/cm³	8.2318×10⁻⁴ g/cm³	1375 J/g
–30 °C	119.6 kPa	0.67764 g/cm³	1.0386×10⁻³ g/cm³	1361 J/g
–25 °C	151.6 kPa	0.67137 g/cm³	1.2969×10⁻³ g/cm³	1345 J/g
–20 °C	190.2 kPa	0.66503 g/cm³	1.6039×10⁻³ g/cm³	1330 J/g
–15 °C	236.3 kPa	0.65854 g/cm³	1.9659×10⁻³ g/cm³	1314 J/g
–10 °C	290.8 kPa	0.65198 g/cm³	2.3874×10⁻³ g/cm³	1297 J/g
–5 °C	354.8 kPa	0.64533 g/cm³	2.8827×10⁻³ g/cm³	1280 J/g
0 °C	429.4 kPa	0.63857 g/cm³	3.4528×10⁻³ g/cm³	1263 J/g
5 °C	515.7 kPa	0.63167 g/cm³	4.1086×10⁻³ g/cm³	1245 J/g
10 °C	614.9 kPa	0.62469 g/cm³	4.8593×10⁻³ g/cm³	1226 J/g
15 °C	728.3 kPa	0.61755 g/cm³	5.7153×10⁻³ g/cm³	1207 J/g
20 °C	857.1 kPa	0.61028 g/cm³	6.6876×10⁻³ g/cm³	1187 J/g
25 °C	1003 kPa	0.60285 g/cm³	7.7882×10⁻³ g/cm³	1167 J/g
30 °C	1166 kPa	0.59524 g/cm³	9.0310×10⁻³ g/cm³	1146 J/g
35 °C	1350 kPa	0.58816 g/cm³	1.0431×10⁻² g/cm³	1124 J/g
40 °C	1554 kPa	0.57948 g/cm³	1.2006×10⁻² g/cm³	1101 J/g
45 °C	1781 kPa	0.57130 g/cm³	1.3775×10⁻² g/cm³	1083 J/g
50 °C	2032 kPa	0.56287 g/cm³	1.5761×10⁻² g/cm³	1052 J/g
55 °C	2310 kPa	0.55420 g/cm³
60 °C	2613 kPa	0.54523 g/cm³	2.05×10⁻² g/cm³
65 °C	2947 kPa	0.53596 g/cm³
70 °C	3312 kPa	0.52632 g/cm³	2.65×10⁻² g/cm³
75 °C	3711 kPa	0.51626 g/cm³
80 °C	4144 kPa	0.50571 g/cm³	3.41×10⁻² g/cm³
85 °C	4614 kPa	0.49463 g/cm³
90 °C	5123 kPa	0.48290 g/cm³	4.39×10⁻² g/cm³
95 °C	5672 kPa	0.47041 g/cm³
100 °C	6264 kPa	0.45693 g/cm³	5.68×10⁻² g/cm³
Temp.	Pressure	ρ of liquid	ρ of vapor	Δ_vapH
The table above gives properties of the vapor–liquid equilibrium of anhydrous ammonia at various temperatures. The second column is vapor pressure in kPa. The third column is the density of the liquid phase. The fourth column is the density of the vapor. The fifth column is the heat of vaporization needed to convert one gram of liquid to vapor.

Freezing curve of ammonia-water system. Three eutectic points I. II. and III. are shown. Left of the I. point the frozen component is ice. Right of the III. point the frozen component is ammonia.^[4]

Vapor over Aqueous Ammonia Solution^[5]
Temp.	%wt NH₃	Partial Pressure NH₃	Partial Pressure H₂O
0 °C	4.72	1.52 kPa	0.68 kPa
	9.15	3.31 kPa	0.71 kPa
	14.73	6.84 kPa	0.55 kPa
	19.62	11.0 kPa	0.40 kPa
	22.90	14.9 kPa	0.37 kPa
10 °C	4.16	2.20 kPa	1.21 kPa
	8.26	4.96 kPa	1.17 kPa
	12.32	8.56 kPa	1.01 kPa
	15.88	12.68 kPa	0.93 kPa
	20.54	19.89 kPa	0.83 kPa
	21.83	22.64 kPa	0.73 kPa
19.9 °C	4.18	3.65 kPa	2.19 kPa
	6.50	6.11 kPa	2.15 kPa
	6.55	6.13 kPa	2.13 kPa
	7.72	7.49 kPa	2.08 kPa
	10.15	10.75 kPa	2.01 kPa
	10.75	11.51 kPa	1.96 kPa
	16.64	22.14 kPa	1.72 kPa
	19.40	28.74 kPa	1.64 kPa
	23.37	40.32 kPa	1.37 kPa
30.09 °C	3.93	5.49 kPa	4.15 kPa
	7.43	11.51 kPa	3.89 kPa
	9.75	16.00 kPa	3.80 kPa
	12.77	23.33 kPa	3.55 kPa
	17.76	38.69 kPa	3.31 kPa
	17.84	38.81 kPa	3.24 kPa
	21.47	53.94 kPa	2.95 kPa
40 °C	3.79	8.15 kPa	7.13 kPa
	7.36	17.73 kPa	6.76 kPa
	11.06	29.13 kPa	6.55 kPa
	15.55	47.14 kPa	5.52 kPa
	17.33	57.02 kPa
	20.85	76.81 kPa	5.04 kPa
50 °C	3.29	10.54 kPa	11.95 kPa
	5.90	20.17 kPa	11.61 kPa
	8.91	32.88 kPa	11.07 kPa
	11.57	45.56 kPa	10.75 kPa
	14.15	60.18 kPa	10.27 kPa
	14.94	64.94 kPa	10.03 kPa
60 °C	3.86	18.25 kPa	19.21 kPa
	5.77	28.78 kPa
	7.78	40.05 kPa	18.47 kPa
	9.37	50.09 kPa	18.07 kPa
	9.37	63.43 kPa	17.39 kPa
Temp.	%wt NH₃	Partial Pressure NH₃	Partial Pressure H₂O

Heat capacity of liquid and vapor

Heat capacity, c_p, of anhydrous ammonia gas. Uses polynomial obtained from CHERIC.^[6]

Heat capacity of anhydrous liquid ammonia. Uses polynomial obtained from CHERIC.^[6]

Spectral data

UV-Vis
λ_max	None nm
Extinction coefficient, ε	None
IR
Major absorption bands	3444, 3337, 1627, 950 cm⁻¹
NMR
Proton NMR
Carbon-13 NMR	None - no carbons
Other NMR data
MS
Masses of main fragments	17 (100%) 16(80%) 15(9%)

Regulatory data

Regulatory data
EINECS number	231-635-3 (gas) 215-647-6 (soln.)
EU index number	007-001-00-5 (gas) 007-001-01-2 (soln.)
PEL-TWA (OSHA)	50 ppm (35 mg/m³)
IDLH (NIOSH)	300 ppm
Flash point	11 °C
Autoignition temperature	651 °C
Explosive limits	15–28%
RTECS #	BO0875000

Safety data sheet

The handling of this chemical may incur notable safety precautions... It is highly recommend that you seek the Safety Data Sheet (SDS) for this chemical from a reliable source and follow its directions.

SIRI
Science Stuff (Ammonia Solution)

References

Linstrom, P.J.; Mallard, W.G. (eds.) NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology, Gaithersburg MD. http://webbook.nist.gov

1 2 CRC Handbook of Chemistry and Physics, 94th ed. http://www.hbcpnetbase.com. Page 9-26. Retrieved 18 June 2013.
↑ Lange's Handbook of Chemistry, 10th ed. page 1436
↑ Lange's Handbook of Chemistry, 10th ed. page 1451 and 1468
↑ Friedrich Merkel, Franjo Bošnjaković (1929). Diagramme und Tabellen zur Berechnung der Absorptions-Kältemachienen. Berlin: Julius Springer. p. 46.
↑ Perman, Jour. Chem. Soc. 83 1168 (1903)
1 2 "Pure Components Properties" (Queriable database). Chemical Engineering Research Information Center. Archived from the original on 3 June 2007. Retrieved 1 June 2007.

Except where noted otherwise, data relate to standard ambient temperature and pressure.

Disclaimer applies.

External links

IR spectrum (from NIST)

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