# 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) |
| Bond angle | 106.7° (H–N–H) |
| Bond strength | 435 kJ/mol (H–NH$_2$) |
| Crystal data ||
| Crystal structure | ? |
| Properties ||
| Dipole moment | 1.46 D |
| Dielectric constant | 22 ε$_0$ at 239 K |
| Magnetic susceptibility | diamagnetic |
| Acidity of NH$_4$$^+$ (pK$_a$) | 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 change of fusion, Δ$_{fus}$H$^o$ | +5.653 kJ/mol |
| Std entropy change of fusion, Δ$_{fus}$S$^o$ | +28.93 J/(mol·K) |
| Std enthalpy change of vaporization, Δ$_{vap}$H$^o$ | +23.35 kJ/mol at BP of −33.4 °C |
| Std entropy change of vaporization, Δ$_{vap}$S$^o$ | +97.41 J/(mol·K) at BP of −33.4 °C |
| Solid properties ||
| Std enthalpy change of formation, Δ$_f$H$^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$_f$H$^o$$_{liquid}$ | −80.882 ± 0.053 kJ/mol |
| Standard molar entropy, S$^o$$_{liquid}$ | ? J/(mol K) |
| Heat capacity, c$_p$ | 80.80 J/(mol K) |
| Gas properties ||
| Std enthalpy change of formation, Δ$_f$H$^o$$_{gas}$ | −45.556 ± 0.029 kJ/mol |
| Std Gibbs free energy change of formation, Δ$_f$G$^o$$_{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 L$^2$ kPa/mol$^2$ b = 0.03707 L/mol |

## Vapor–liquid equilibrium data

| P in mm Hg | P in mm Hg | 1 | 10 | 40 | 100 | 400 | 760 | 1520 | 3800 | 7600 | 15600 | 30400 | 45600 |
| T in °C | 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:
    log$_{10}$P = 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 :
| Temp. | Pressure | ρ of liquid | ρ of vapor | Δ$_{vap}$H |
| −78 °C | 5.90 kPa | | |
| −75 °C | 7.93 kPa | 0.73094 g/cm$^3$ | 7.8241×10$^{−5}$ g/cm$^3$ | |
| −70 °C | 10.92 kPa | 0.72527 g/cm$^3$ | 1.1141×10$^{−4}$ g/cm$^3$ | |
| −65 °C | 15.61 kPa | 0.71953 g/cm$^3$ | 1.5552×10$^{−4}$ g/cm$^3$ | |
| −60 °C | 21.90 kPa | 0.71378 g/cm$^3$ | 2.1321×10$^{−4}$ g/cm$^3$ | |
| −55 °C | 30.16 kPa | 0.70791 g/cm$^3$ | 2.8596×10$^{−4}$ g/cm$^3$ | |
| −50 °C | 40.87 kPa | 0.70200 g/cm$^3$ | 3.8158×10$^{−4}$ g/cm$^3$ | 1417 J/g |
| −45 °C | 54.54 kPa | 0.69604 g/cm$^3$ | 4.9940×10$^{−4}$ g/cm$^3$ | 1404 J/g |
| −40 °C | 71.77 kPa | 0.68999 g/cm$^3$ | 6.4508×10$^{−4}$ g/cm$^3$ | 1390 J/g |
| −35 °C | 93.19 kPa | 0.68385 g/cm$^3$ | 8.2318×10$^{−4}$ g/cm$^3$ | 1375 J/g |
| −30 °C | 119.6 kPa | 0.67764 g/cm$^3$ | 1.0386×10$^{−3}$ g/cm$^3$ | 1361 J/g |
| −25 °C | 151.6 kPa | 0.67137 g/cm$^3$ | 1.2969×10$^{−3}$ g/cm$^3$ | 1345 J/g |
| −20 °C | 190.2 kPa | 0.66503 g/cm$^3$ | 1.6039×10$^{−3}$ g/cm$^3$ | 1330 J/g |
| −15 °C | 236.3 kPa | 0.65854 g/cm$^3$ | 1.9659×10$^{−3}$ g/cm$^3$ | 1314 J/g |
| −10 °C | 290.8 kPa | 0.65198 g/cm$^3$ | 2.3874×10$^{−3}$ g/cm$^3$ | 1297 J/g |
| −5 °C | 354.8 kPa | 0.64533 g/cm$^3$ | 2.8827×10$^{−3}$ g/cm$^3$ | 1280 J/g |
| 0 °C | 429.4 kPa | 0.63857 g/cm$^3$ | 3.4528×10$^{−3}$ g/cm$^3$ | 1263 J/g |
| 5 °C | 515.7 kPa | 0.63167 g/cm$^3$ | 4.1086×10$^{−3}$ g/cm$^3$ | 1245 J/g |
| 10 °C | 614.9 kPa | 0.62469 g/cm$^3$ | 4.8593×10$^{−3}$ g/cm$^3$ | 1226 J/g |
| 15 °C | 728.3 kPa | 0.61755 g/cm$^3$ | 5.7153×10$^{−3}$ g/cm$^3$ | 1207 J/g |
| 20 °C | 857.1 kPa | 0.61028 g/cm$^3$ | 6.6876×10$^{−3}$ g/cm$^3$ | 1187 J/g |
| 25 °C | 1003 kPa | 0.60285 g/cm$^3$ | 7.7882×10$^{−3}$ g/cm$^3$ | 1167 J/g |
| 30 °C | 1166 kPa | 0.59524 g/cm$^3$ | 9.0310×10$^{−3}$ g/cm$^3$ | 1146 J/g |
| 35 °C | 1350 kPa | 0.58816 g/cm$^3$ | 1.0431×10$^{−2}$ g/cm$^3$ | 1124 J/g |
| 40 °C | 1554 kPa | 0.57948 g/cm$^3$ | 1.2006×10$^{−2}$ g/cm$^3$ | 1101 J/g |
| 45 °C | 1781 kPa | 0.57130 g/cm$^3$ | 1.3775×10$^{−2}$ g/cm$^3$ | 1083 J/g |
| 50 °C | 2032 kPa | 0.56287 g/cm$^3$ | 1.5761×10$^{−2}$ g/cm$^3$ | 1052 J/g |
| 55 °C | 2310 kPa | 0.55420 g/cm$^3$ | | |
| 60 °C | 2613 kPa | 0.54523 g/cm$^3$ | 2.05×10$^{−2}$ g/cm$^3$ | |
| 65 °C | 2947 kPa | 0.53596 g/cm$^3$ | | |
| 70 °C | 3312 kPa | 0.52632 g/cm$^3$ | 2.65×10$^{−2}$ g/cm$^3$ | |
| 75 °C | 3711 kPa | 0.51626 g/cm$^3$ | | |
| 80 °C | 4144 kPa | 0.50571 g/cm$^3$ | 3.41×10$^{−2}$ g/cm$^3$ | |
| 85 °C | 4614 kPa | 0.49463 g/cm$^3$ | | |
| 90 °C | 5123 kPa | 0.48290 g/cm$^3$ | 4.39×10$^{−2}$ g/cm$^3$ | |
| 95 °C | 5672 kPa | 0.47041 g/cm$^3$ | | |
| 100 °C | 6264 kPa | 0.45693 g/cm$^3$ | 5.68×10$^{−2}$ g/cm$^3$ | |
| Temp. | Pressure | ρ of liquid | ρ of vapor | Δ$_{vap}$H |
| 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 solution :
| Temp. | %wt NH$_3$ | Partial pressure NH$_3$ | Partial pressure H$_2$O |
| 0 °C | 4.72 | 1.52 kPa | 0.68 kPa |
| 0 °C | 9.15 | 3.31 kPa | 0.71 kPa |
| 0 °C | 14.73 | 6.84 kPa | 0.55 kPa |
| 0 °C | 19.62 | 11.0 kPa | 0.40 kPa |
| 0 °C | 22.90 | 14.9 kPa | 0.37 kPa |
| 10 °C | 4.16 | 2.20 kPa | 1.21 kPa |
| 10 °C | 8.26 | 4.96 kPa | 1.17 kPa |
| 10 °C | 12.32 | 8.56 kPa | 1.01 kPa |
| 10 °C | 15.88 | 12.68 kPa | 0.93 kPa |
| 10 °C | 20.54 | 19.89 kPa | 0.83 kPa |
| 10 °C | 21.83 | 22.64 kPa | 0.73 kPa |
| 19.9 °C | 4.18 | 3.65 kPa | 2.19 kPa |
| 19.9 °C | 6.50 | 6.11 kPa | 2.15 kPa |
| 19.9 °C | 6.55 | 6.13 kPa | 2.13 kPa |
| 19.9 °C | 7.72 | 7.49 kPa | 2.08 kPa |
| 19.9 °C | 10.15 | 10.75 kPa | 2.01 kPa |
| 19.9 °C | 10.75 | 11.51 kPa | 1.96 kPa |
| 19.9 °C | 16.64 | 22.14 kPa | 1.72 kPa |
| 19.9 °C | 19.40 | 28.74 kPa | 1.64 kPa |
| 19.9 °C | 23.37 | 40.32 kPa | 1.37 kPa |
| 30.09 °C | 3.93 | 5.49 kPa | 4.15 kPa |
| 30.09 °C | 7.43 | 11.51 kPa | 3.89 kPa |
| 30.09 °C | 9.75 | 16.00 kPa | 3.80 kPa |
| 30.09 °C | 12.77 | 23.33 kPa | 3.55 kPa |
| 30.09 °C | 17.76 | 38.69 kPa | 3.31 kPa |
| 30.09 °C | 17.84 | 38.81 kPa | 3.24 kPa |
| 30.09 °C | 21.47 | 53.94 kPa | 2.95 kPa |
| 40 °C | 3.79 | 8.15 kPa | 7.13 kPa |
| 40 °C | 7.36 | 17.73 kPa | 6.76 kPa |
| 40 °C | 11.06 | 29.13 kPa | 6.55 kPa |
| 40 °C | 15.55 | 47.14 kPa | 5.52 kPa |
| 40 °C | 17.33 | 57.02 kPa | |
| 40 °C | 20.85 | 76.81 kPa | 5.04 kPa |
| 50 °C | 3.29 | 10.54 kPa | 11.95 kPa |
| 50 °C | 5.90 | 20.17 kPa | 11.61 kPa |
| 50 °C | 8.91 | 32.88 kPa | 11.07 kPa |
| 50 °C | 11.57 | 45.56 kPa | 10.75 kPa |
| 50 °C | 14.15 | 60.18 kPa | 10.27 kPa |
| 50 °C | 14.94 | 64.94 kPa | 10.03 kPa |
| 60 °C | 3.86 | 18.25 kPa | 19.21 kPa |
| 60 °C | 5.77 | 28.78 kPa | |
| 60 °C | 7.78 | 40.05 kPa | 18.47 kPa |
| 60 °C | 9.37 | 50.09 kPa | 18.07 kPa |
| 60 °C | 9.37 | 63.43 kPa | 17.39 kPa |
| Temp. | %wt NH$_3$ | Partial Pressure NH$_3$ | Partial Pressure H$_2$O |

## Heat capacity of liquid and vapor

* Heat capacity, c$_p$, of anhydrous ammonia gas. Uses polynomial obtained from CHERIC.
* Heat capacity of anhydrous liquid ammonia. Uses polynomial obtained from CHERIC.

## 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/m$^3$) |
| 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)