Properties of Hydrogen

Hydrogen is the only element that is not a member of any family in the periodic table. Because of its Is electron configuration, it is generally placed above lithium in the table. However, it is definitely not an alkali metal. It forms a positive ion much less readily than any alkali metal. The ionization energy of the hydrogen atom is 1312 kj/mol, whereas that of lithium is 520 kj/mol. 

Elemental hydrogen exists at room temperature as a colorless, odorless, tasteless gas composed of diatomic molecules. We can call H2 dthydrogen, but it is more commonly referred to as either molecular hydrogen or simply hydrogen. Because H2 is nonpolar and has only two electrons, attractive forces between molecules are extremely weak. As a result, its melting point (—259 °C) and boiling point (—253 °C) are very low. 

The H — H bond enthalpy (436 kJ/mol) is high for a single bond. = (Table 8.4) By comparison, the Cl— Cl bond enthalpy is only 242 kj/mol. Because H2 has a strong bond, most reactions involving H2 are slow at room temperature. However, the molecule is readily activated by heat, irradiation, or catalysis. The activation generally produces hydrogen atoms, which are very reactive. Once H2 is activated, it reacts rapidly and exothermically with a wide variety of substances. 

If H2 is activated to produce H, what must the other product be  

Heat of combustion, gross (including thermal energy 286.0 kJ/mol 

Various property data of hydrogen are summarized in Table 8-1. A more detailed description of the properties is given, e.g., in [45, 120]. 

H2 was first recognized as a substance in 1766 by Henry Cavendish. It is the least dense gas, colorless, odorless, and tasteless. It is flammable and is slightly soluble in water. H2 is a mixture of the para and ortho forms, which differ in their electronic and nuclear spins. At room temperature, atmospheric hydrogen gas (GH2) is a mixture of 75% para-hydrogen and 25% ortho-hydrogen. Some of the properties of H2 are given in Table 1.43. 

GH2 is usually stored and transported at very high pressures, whereas LH2 is stored at very low temperatures. The temperature of cryogenic LH2 under atmospheric pressure is under -253°C (-423.2°F). The pressure of compressed GH2 ranges from 350 to 800 bar (5,000 to 12,000 psig or 34.5 to 82.7 mPa). 

Because of the lack of an international standardization of units, Table 1.44 provides some conversion factors among the various units used in defining the process properties of H2. 

Post-Oil Energy Technology After the Age of Fossil Fuels 

Conversion among Units of Pressure, Temperature, and Energy 

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Table 11. Properties of Hydrogen of Interest in Safety Considerations...

R. D. McCarty,. Hord, H. M. Roder, S elected Properties of Hydrogen (Engineering Design Data). U.S. Dept, of Commerce, National Bureau of Standards, Washington, D.C., 1981, pp. 6—291. 

Hydrogen peroxide is used in many applications throughout a wide variety of industries. The principal use areas are shown in Table 9. Most ate based on the oxidizing properties of hydrogen peroxide. Some are derived from substitution, decomposition, or the formation of perhydrates. 

Physical Properties. Hydrogen sulfide, H2S, is a colorless gas having a characteristic rotten-egg odor. The physical properties of hydrogen sulfide are given in Table 2. 

Table 2. Physical and Thermodynamic Properties of Hydrogen Sulfide...

The physical properties of hydrogen cyanide are Hsted in Table 1. 

Table 4. Nuclear Magnetic Resonance Properties of Hydrogen Isotopes...

Three eheinieal properties of hydrogen cyanide eontribute to tlie potential for an aeeidental release of the eheinieal. "... 

TABLE 8.5.1 Physical Properties of Hydrogen Fluoride CAS Registry Number 07664-39-3... 

State tlie two most significant chemical properties of hydrogen fluoride contributing to tlie potential for release. 

H. Cavendish established the true properties of hydrogen by reacting several acids with iron, zinc and tin he showed that it was much lighter than air. 

Table 3.1 Atomic properties of hydrogen (protium), deuterium, and tritium...

Table 14,11 Some physical properties of hydrogen peroxide ...

Mechanical properties of hydrogenated titanium alloys are strongly dependent on the applied stress tensor, especially on its hydrostatic component. This was illustrated by the high-pressure tensile and extrusion tests on the Ti-6Al-2.5Mo-2Cr alloy and the same alloy hydrogenated to a = 0.15 wt.%H. Tests were carried out using the apparatus at the Institute of Metal Physics UD RAS operating at hydrostatic pressures of machine oil to 15 kbax and temperatures to 250°C. 

Table 2 shows some safety-related physical properties of hydrogen as compared to two commonly accepted fuels, natural gas and gasoline. 

Safety-Related Properties of Hydrogen, Methane, and Gasoline... 

Nesbitt, L. E., et al., Properties of hydrogen sulfide scavengers used in water-based drilling fluids, Proceedings of 36th Annual Technical Meeting of the Petroleum Society, Edmonton, Canada, June 2-5, 1985. 

Selected Properties of Hydrogen, Important Ci-Cio Paraffins, Methylcyclopentane and Cyclohexane ... 

TABLE 14.2 Chemical Properties of Hydrogen Reactant Reaction with hydrogen ... 

Sel f-Test 14.3B What are some of the properties of hydrogen that argue against its classification as a Croup 1 element ... 

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