Vapor pressure of hydrogen at different temperatures

Vapor pressure of hydrogen at different temperatures

Junjie Chen

Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China

Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com

Hydrogen is a colourless, odourless, tasteless, flammable gaseous substance that is the simplest member of the family of chemical elements. The hydrogen atom has a nucleus consisting of a proton bearing one unit of positive electrical charge; an electron, bearing one unit of negative electrical charge, is also associated with this nucleus. Under ordinary conditions, hydrogen gas is a loose aggregation of hydrogen molecules, each consisting of a pair of atoms, a diatomic molecule. The earliest known important chemical property of hydrogen is that it burns with oxygen to form water; indeed, the name hydrogen is derived from Greek words meaning maker of water. Elementary hydrogen finds its principal industrial application in the manufacture of ammonia and in the hydrogenation of carbon monoxide and organic compounds. The extremely low melting and boiling points result from weak forces of attraction between the molecules. The existence of these weak intermolecular forces is also revealed by the fact that, when hydrogen gas expands from high to low pressure at room temperature, its temperature rises, whereas the temperature of most other gases falls. According to thermodynamic principles, this implies that repulsive forces exceed attractive forces between hydrogen molecules at room temperature, otherwise, the expansion would cool the hydrogen. In fact, at a temperature of -68.6 degrees Celsius, attractive forces predominate, and hydrogen, therefore, cools upon being allowed to expand below that temperature. The cooling effect becomes so pronounced at temperatures below that of liquid nitrogen that the effect is utilized to achieve the liquefaction temperature of hydrogen gas itself.

Temperature (degrees kelvin), Pressure (kilopascals)

14                               7.884

14.5                                   10.38

15                               13.43

15.5                                   17.13

16                               21.55

16.5                                   26.77

17                               32.89

17.5                                   39.98

18                               48.15

18.5                                   57.48

19                               68.07

19.5                                   80.02

20                               93.41

20.5                                   108.4

21                               125

21.5                                   143.3

22                               163.5

22.5                                   185.6

23                               209.8

23.5                                   236.2

24                               264.8

24.5                                   295.7

25                               329.2

25.5                                   365.2

26                               403.8

26.5                                   445.3

27                               489.6

27.5                                   537

28                               587.5

28.5                                   641.2

29                               698.3

29.5                                   758.9

30                               823.2

30.5                                   891.2

31                               963.3

31.5                                   1040

32                               1120

32.5                                   1206

Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China