This page provides supplementary chemical data on ammonia. Structure and properties
Molecular structure Point group C3v Bond length 101.2 pm (N–H)CRC Handbook of Chemistry and Physics, 94th ed. http://www.hbcpnetbase.com . Page 9-26. Retrieved 18 June 2013. Bond angle 106.7° (H–N–H) 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 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 changeof fusion, ΔfusHo +5.653 kJ/mol Std entropy changeof fusion, ΔfusSo +28.93 J/(mol·K) Std enthalpy changeof vaporization, ΔvapHo +23.35 kJ/mol at BP of −33.4 °C Std entropy changeof vaporization, ΔvapSo +97.41 J/(mol·K) at BP of −33.4 °C Solid properties Std enthalpy changeof formation, ΔfHosolid ? kJ/mol Standard molar entropy,Sosolid ? J/(mol K) Heat capacity, cp ? J/(mol K) Liquid properties Std enthalpy changeof formation, ΔfHoliquid −80.882 ± 0.053 kJ/mol"Ammonia - NH3 (aq, undissoc)" Active Thermochemical Tables v1.130. https://atct.anl.gov/Thermochemical%20Data/version%201.130/species/?species_number=1041 Standard molar entropy,Soliquid ? J/(mol K) Heat capacity, cp 80.80 J/(mol K) Gas properties Std enthalpy changeof formation, ΔfHogas −45.556 ± 0.029 kJ/mol"Ammonia - NH3(g)" Active Thermochemical Tables v1.130. https://atct.anl.gov/Thermochemical%20Data/version%201.130/species/?species_number=35 Std Gibbs free energy changeof 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, γat 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 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.
Vapor-pressure formula for ammonia:Lange's Handbook of Chemistry, 10th ed. page 1436.
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 ammoniaLange's Handbook of Chemistry, 10th ed. page 1451 and 1468. Temp. Pressure ρ of liquid ρ of vapor ΔvapH −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 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. Vapor over aqueous ammonia solutionPerman, Jour. Chem. Soc. 83 1168 (1903). Temp. %wt NH3 Partial pressureNH3 Partial pressureH2O 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 PressureNH3 Partial PressureH2O
Heat capacity of liquid and vapor
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. SIRI Science Stuff (Ammonia Solution)
References
External links Phase diagram for ammonia IR spectrum (from NIST)