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By the end of this section, you will be able to:
  • Describe the properties, preparation, and compounds of hydrogen

Hydrogen is the most abundant element in the universe. The sun and other stars are composed largely of hydrogen. Astronomers estimate that 90% of the atoms in the universe are hydrogen atoms. Hydrogen is a component of more compounds than any other element. Water is the most abundant compound of hydrogen found on earth. Hydrogen is an important part of petroleum, many minerals, cellulose and starch, sugar, fats, oils, alcohols, acids, and thousands of other substances.

At ordinary temperatures, hydrogen is a colorless, odorless, tasteless, and nonpoisonous gas consisting of the diatomic molecule H 2 . Hydrogen is composed of three isotopes, and unlike other elements, these isotopes have different names and chemical symbols: protium, 1 H, deuterium, 2 H (or “D”), and tritium 3 H (or “T”). In a naturally occurring sample of hydrogen, there is one atom of deuterium for every 7000 H atoms and one atom of radioactive tritium for every 10 18 H atoms. The chemical properties of the different isotopes are very similar because they have identical electron structures, but they differ in some physical properties because of their differing atomic masses. Elemental deuterium and tritium have lower vapor pressure than ordinary hydrogen. Consequently, when liquid hydrogen evaporates, the heavier isotopes are concentrated in the last portions to evaporate. Electrolysis of heavy water, D 2 O, yields deuterium. Most tritium originates from nuclear reactions.

Preparation of hydrogen

Elemental hydrogen must be prepared from compounds by breaking chemical bonds. The most common methods of preparing hydrogen follow.

From steam and carbon or hydrocarbons

Water is the cheapest and most abundant source of hydrogen. Passing steam over coke (an impure form of elemental carbon) at 1000 °C produces a mixture of carbon monoxide and hydrogen known as water gas:

C ( s ) + H 2 O ( g ) 1000 °C CO ( g ) + H 2 ( g ) water gas

Water gas is as an industrial fuel. It is possible to produce additional hydrogen by mixing the water gas with steam in the presence of a catalyst to convert the CO to CO 2 . This reaction is the water gas shift reaction.

It is also possible to prepare a mixture of hydrogen and carbon monoxide by passing hydrocarbons from natural gas or petroleum and steam over a nickel-based catalyst. Propane is an example of a hydrocarbon reactant:

C 3 H 8 ( g ) + 3 H 2 O ( g ) catalyst 900 °C 3CO ( g ) + 7 H 2 ( g )


Hydrogen forms when direct current electricity passes through water containing an electrolyte such as H 2 SO 4 , as illustrated in [link] . Bubbles of hydrogen form at the cathode, and oxygen evolves at the anode. The net reaction is:

2H 2 O ( l ) + electrical energy 2H 2 ( g ) + O 2 ( g )
A diagram shows a beaker that contains a liquid, a battery submerged in the liquid, and two test tubes. The battery has the positive and negative terminals labeled. The liquid is connected by a right-facing arrow to an image of two molecules made up of one red atom and two white atoms. It is labeled, “Water,” and, “2 H subscript 2 O ( l ).” The left test tube above the negative sign is connected by a right-facing arrow to an image of two pairs of white atoms. The image is labeled, “Hydrogen,” and, “2 H subscript 2 ( g ).” The right test tube above the positive sign is connected by a right-facing arrow to an image of a pair of red atoms. The image is labeled, “Oxygen,” and, “O subscript 2 ( g ).”
The electrolysis of water produces hydrogen and oxygen. Because there are twice as many hydrogen atoms as oxygen atoms and both elements are diatomic, there is twice the volume of hydrogen produced at the cathode as there is oxygen produced at the anode.

Reaction of metals with acids

This is the most convenient laboratory method of producing hydrogen. Metals with lower reduction potentials reduce the hydrogen ion in dilute acids to produce hydrogen gas and metal salts. For example, as shown in [link] , iron in dilute hydrochloric acid produces hydrogen gas and iron(II) chloride:

Questions & Answers

white phosphorus reacts with caustic soda
Graham Reply
covalent bond and ionic bond
Chikwado Reply
so what should we do
If 0.5 mole of a monoalkanoic acid weighs 44g, determine the molecular formula and the name of the acid. (H=1,C=12,O=16)
Benson Reply
given that 32.og sulphur contains 6.02×10 ^23 sulphur atoms how many atoms are there in 2.70g of aluminum. (A=27 s =32 )
Faith Reply
Correct 👍... Its 1/10 of the mass number of Al which is 27
show the steps pls
2.7g of Al - 6.02×10^23×2.7/27=0.602×10^23
An aqueos solution of sodium hydroxide containing 2g in 200cm3 of solution has a concentration of (NaOH=40).
0.25 mol/dm3
what is the meaning of the term an orbital?
syopi Reply
Orbital mathematical function that describes the wave-like behavior of an electron, electron pair, or (less commonly) nucleons. An orbital may also be called an atomic orbital or electron
orbitals describe where an electron is likely to be found in an atom. Molecular orbitals perform the same role in molecules
why is alkynes more reactive than alkenes and alkanes
Bernice Reply
Alkenes and alkynes are generally more reactive than alkanes due to the electron density available in their pi bonds.
What are molecules
Ruth Reply
a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
were is ruth
what is partial pressure law
Mokutmfon Reply
what is the structural formular for 2,3-dimethylbutane?
Mercy Reply
name the following compound (COOH)2
CH3-CH(CH3)-CH(CH3)-CH3 this is 2,3-dimethylbutane
(COOH)2 is oxalic acid
what is chemistry
Boris Reply
chemistry is the study of chemical reactions
Chemistry is the study of matter, its properties, how and why substances combine or separate to form other substances, and how substances interact with energy.
chemistry is the study of matter, it's properties and composition
am from Abuja and am in ss1
ss1 some one translate that for me we use grades in my country
maybe grade 9
okay am a chemistry and biology teacher from Zambia
should be grade 10 I think
thats good Mr mwanza
harriet you in grade what
GCE 12
yes sir
me ss2
so are a final year student
What is the chemical formula for alcohol? is the chemical formula for alcohol?
Grant Reply
20 element are what element?
Eric Reply
What is Chemistry?
Esther Reply
studying about chemical reactions
You are right Vengada
studying about the rate of chemical is ?
Chemistry is the branch of sciences dealing with the composition of substances and their properties and reaction.
chemical reaction is the process in which one or more chemical substances react with other chemical substance and converted one or more different substances.
what is isotopy
Isotopy is one of two or more atoms having the same atomic numbers but different mass number.
is phenomenon where by atom of an element exhibit different mass number but have the same atomic number
same number of electrons and protons but different number of neutrons
is an atom which has different number of protons but same number of electron such as carbon -12 and corbon 12
carbon-12 and carbon-13 have 6 electrons and 6 protons but carbon-12 has 6 neutrons and carbon-13 has 7 neutrons. Isotopes have different amount of neutrons
Practice Key Terms 3

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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