Vapor pressure of hydrogen at different temperatures

<strong>Vapor pressure of hydrogen at different temperatures</strong> 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: [e-mail] 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: [e-mail], Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China