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  2. Hydrogen - Wikipedia

    en.wikipedia.org/wiki/Hydrogen

    Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest element and, at standard conditions, is a gas of diatomic molecules with the formula H 2, sometimes called dihydrogen, [11] hydrogen gas, molecular hydrogen, or simply hydrogen. It is colorless, odorless, [12] non-toxic, and highly combustible.

  3. Hydrogen atom - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_atom

    A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral hydrogen atom contains a single positively charged proton in the nucleus, and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. [1]

  4. Standard enthalpy of formation - Wikipedia

    en.wikipedia.org/wiki/Standard_enthalpy_of_formation

    Monatomic hydrogen Gas H 218 Hydrogen: Gas H 2: 0 Water: Gas H 2 O −241.818 Water: Liquid H 2 O −285.8 Hydrogen ion: Aqueous H + 0 Hydroxide ion: Aqueous OH −: −230 Hydrogen peroxide: Liquid H 2 O 2: −187.8 Phosphoric acid: Liquid H 3 PO 4: −1288 Hydrogen cyanide: Gas HCN 130.5 Hydrogen bromide: Liquid HBr −36.3 Hydrogen chloride ...

  5. Vapour density - Wikipedia

    en.wikipedia.org/wiki/Vapour_density

    Vapour density is the density of a vapour in relation to that of hydrogen. It may be defined as mass of a certain volume of a substance divided by mass of same volume of hydrogen. vapour density = mass of n molecules of gas / mass of n molecules of hydrogen gas . vapour density = molar mass of gas / molar mass of H 2

  6. Hydrogen evolution reaction - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_evolution_reaction

    In acidic conditions, the hydrogen evolution reaction follows the formula: [6] 2 H + + 2 e − → H 2. In neutral or alkaline conditions, the reaction follows the formula: [6] 4 H 2 O + 4 e − → 2 H 2 + 4 HO −. Both of these mechanisms can be seen in industrial practices at the cathode side of the electrolyzer where hydrogen evolution occurs.

  7. Standard Gibbs free energy of formation - Wikipedia

    en.wikipedia.org/wiki/Standard_Gibbs_free_energy...

    The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).

  8. Liquid hydrogen - Wikipedia

    en.wikipedia.org/wiki/Liquid_hydrogen

    Liquid hydrogen (H 2 (l)) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H 2 form. [4] To exist as a liquid, H 2 must be cooled below its critical point of 33 K. However, for it to be in a fully liquid state at atmospheric pressure, H 2 needs to be cooled to 20.28 K (−252.87 °C; −423.17 °F). [5]

  9. Chemical equation - Wikipedia

    en.wikipedia.org/wiki/Chemical_equation

    A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and chemical formulas.The reactant entities are given on the left-hand side and the product entities are on the right-hand side with a plus sign between the entities in both the reactants and the products, and an arrow that points towards the products to show the direction of the reaction. [1]