Ammonia (data page)

This page provides supplementary chemical data on ammonia.

Structure and properties
Molecular structure
Point group C3v
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+ (pKa) 9.25

Thermodynamic properties
Phase diagram and crystalline states of ammonia
I. cubic, II. hcp, III. fcc, IV. orthorhombic
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, ΔfusHo		 +5.653 kJ/mol
Std entropy change
of fusion, ΔfusSo		 +28.93 J/(mol·K)
Std enthalpy change
of vaporization, ΔvapHo		 +23.35 kJ/mol at BP of −33.4 °C
Std entropy change
of vaporization, ΔvapSo		 +97.41 J/(mol·K) at BP of −33.4 °C
Solid properties
Std enthalpy change
of formation, ΔfHosolid		  ? kJ/mol
Standard molar entropy,
Sosolid		  ? J/(mol K)
Heat capacity, cp  ? J/(mol K)
Liquid properties
Std enthalpy change
of formation, ΔfHoliquid		  ? kJ/mol
Standard molar entropy,
Soliquid		  ? J/(mol K)
Heat capacity, cp 80.80 J/(mol K)
Gas properties
Std enthalpy change
of formation, ΔfHogas		 −45.92 kJ/mol
Std Gibbs free energy change
of formation, ΔfGogas		 −16.6 kJ/mol
Standard molar entropy,
Sogas		 192.77 J/(mol K)
Heat capacity, cp 35.06 J/(mol K)
Heat capacity ratio, γ
at 15 °C		 1.310
van der Waals' constants a = 422.5 L2 kPa/mol2
b = 0.03707 L/mol

Vapor–liquid equilibrium data
P in mm Hg11040100 400760152038007600156003040045600
T in °C−109.1(s)−91.9(s)−79.2(s)−68.4−45.4−33.6−18.74.725.750.178.998.3

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]

log10P = A – B / (T − C),

where P is pressure in kPa, and T is temperature in kelvins;

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 ΔvapH
−78 °C5.90 kPa
−75 °C7.93 kPa 0.73094 g/cm3 7.8241×10−5 g/cm3
−70 °C10.92 kPa 0.72527 g/cm3 1.1141×10−4 g/cm3
−65 °C15.61 kPa 0.71953 g/cm3 1.5552×10−4 g/cm3
−60 °C21.90 kPa 0.71378 g/cm3 2.1321×10−4 g/cm3
−55 °C30.16 kPa 0.70791 g/cm3 2.8596×10−4 g/cm3
−50 °C40.87 kPa 0.70200 g/cm3 3.8158×10−4 g/cm3 1417 J/g
−45 °C54.54 kPa 0.69604 g/cm3 4.9940×10−4 g/cm3 1404 J/g
−40 °C71.77 kPa 0.68999 g/cm3 6.4508×10−4 g/cm3 1390 J/g
−35 °C93.19 kPa 0.68385 g/cm3 8.2318×10−4 g/cm3 1375 J/g
−30 °C119.6 kPa 0.67764 g/cm3 1.0386×10−3 g/cm3 1361 J/g
−25 °C151.6 kPa 0.67137 g/cm3 1.2969×10−3 g/cm3 1345 J/g
−20 °C190.2 kPa 0.66503 g/cm3 1.6039×10−3 g/cm3 1330 J/g
−15 °C236.3 kPa 0.65854 g/cm3 1.9659×10−3 g/cm3 1314 J/g
−10 °C290.8 kPa 0.65198 g/cm3 2.3874×10−3 g/cm3 1297 J/g
−5 °C354.8 kPa 0.64533 g/cm3 2.8827×10−3 g/cm3 1280 J/g
 0 °C429.4 kPa 0.63857 g/cm3 3.4528×10−3 g/cm3 1263 J/g
 5 °C515.7 kPa 0.63167 g/cm3 4.1086×10−3 g/cm3 1245 J/g
 10 °C614.9 kPa 0.62469 g/cm3 4.8593×10−3 g/cm3 1226 J/g
 15 °C728.3 kPa 0.61755 g/cm3 5.7153×10−3 g/cm3 1207 J/g
 20 °C857.1 kPa 0.61028 g/cm3 6.6876×10−3 g/cm3 1187 J/g
 25 °C1003 kPa 0.60285 g/cm3 7.7882×10−3 g/cm3 1167 J/g
 30 °C1166 kPa 0.59524 g/cm3 9.0310×10−3 g/cm3 1146 J/g
 35 °C1350 kPa 0.58816 g/cm3 1.0431×10−2 g/cm3 1124 J/g
 40 °C1554 kPa 0.57948 g/cm3 1.2006×10−2 g/cm3 1101 J/g
 45 °C1781 kPa 0.57130 g/cm3 1.3775×10−2 g/cm3 1083 J/g
 50 °C2032 kPa 0.56287 g/cm3 1.5761×10−2 g/cm3 1052 J/g
 55 °C2310 kPa 0.55420 g/cm3
 60 °C2613 kPa 0.54523 g/cm3 2.05×10−2 g/cm3
 65 °C2947 kPa 0.53596 g/cm3
 70 °C3312 kPa 0.52632 g/cm3 2.65×10−2 g/cm3
 75 °C3711 kPa 0.51626 g/cm3
 80 °C4144 kPa 0.50571 g/cm3 3.41×10−2 g/cm3
 85 °C4614 kPa 0.49463 g/cm3
 90 °C5123 kPa 0.48290 g/cm3 4.39×10−2 g/cm3
 95 °C5672 kPa 0.47041 g/cm3
100 °C6264 kPa 0.45693 g/cm3 5.68×10−2 g/cm3
Temp. Pressure ρ of liquid ρ of vapor ΔvapH
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 °C4.721.52 kPa 0.68 kPa
9.153.31 kPa0.71 kPa
14.736.84 kPa0.55 kPa
19.6211.0 kPa0.40 kPa
22.9014.9 kPa0.37 kPa
10 °C4.162.20 kPa 1.21 kPa
8.264.96 kPa1.17 kPa
12.328.56 kPa1.01 kPa
15.8812.68 kPa 0.93 kPa
20.5419.89 kPa 0.83 kPa
21.8322.64 kPa 0.73 kPa
19.9 °C4.183.65 kPa 2.19 kPa
6.506.11 kPa2.15 kPa
6.556.13 kPa2.13 kPa
7.727.49 kPa2.08 kPa
10.1510.75 kPa 2.01 kPa
10.7511.51 kPa 1.96 kPa
16.6422.14 kPa 1.72 kPa
19.4028.74 kPa 1.64 kPa
23.3740.32 kPa 1.37 kPa
30.09 °C3.935.49 kPa 4.15 kPa
7.4311.51 kPa3.89 kPa
9.7516.00 kPa3.80 kPa
12.7723.33 kPa 3.55 kPa
17.7638.69 kPa 3.31 kPa
17.8438.81 kPa 3.24 kPa
21.4753.94 kPa 2.95 kPa
40 °C3.798.15 kPa 7.13 kPa
7.3617.73 kPa6.76 kPa
11.0629.13 kPa 6.55 kPa
15.5547.14 kPa 5.52 kPa
17.3357.02 kPa
20.8576.81 kPa 5.04 kPa
50 °C3.2910.54 kPa 11.95 kPa
5.9020.17 kPa11.61 kPa
8.9132.88 kPa11.07 kPa
11.5745.56 kPa 10.75 kPa
14.1560.18 kPa 10.27 kPa
14.9464.94 kPa 10.03 kPa
60 °C3.8618.25 kPa 19.21 kPa
5.7728.78 kPa
7.7840.05 kPa18.47 kPa
9.3750.09 kPa18.07 kPa
9.3763.43 kPa17.39 kPa
Temp. %wt NH3 Partial Pressure
NH3		 Partial Pressure
H2O

Heat capacity of liquid and vapor
Heat capacity, cp, 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
λmax 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.

References
  • Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD)
  1. CRC Handbook of Chemistry and Physics, 94th ed. http://www.hbcpnetbase.com Archived 24 July 2017 at the Wayback Machine. Page 9-26. Retrieved 18 June 2013.
  2. Lange's Handbook of Chemistry, 10th ed. page 1436.
  3. Lange's Handbook of Chemistry, 10th ed. page 1451 and 1468.
  4. Friedrich Merkel, Franjo Bošnjaković (1929). Diagramme und Tabellen zur Berechnung der Absorptions-Kältemachienen. Berlin: Julius Springer. p. 46.
  5. Perman, Jour. Chem. Soc. 83 1168 (1903).
  6. "Pure Components Properties" (Queriable database). Chemical Engineering Research Information Center. Archived from the original on 3 June 2007. Retrieved 1 June 2007.
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