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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 )

Electrolysis

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

how can someone understand chemistry vividly
Mercy Reply
Maybe by reading proofs or practical work and application in modern world.
Abdelkarim
what is isotopes
Samuel Reply
whats de shape of water
Amara Reply
water has no shape because it's liquid
Wil
water is a shapeless, odourless, colourless and tasteless substance that only takes the shape of its container.
mikefred
i think they're referring to the molecular shape?
It has no shape but takes the shape of the container
kpadonu
what isthe maening pkw
Wilson Reply
introduction to chemistry for beginner
Lansana Reply
hi
noble
through out human history
marwan Reply
Yes?
Esther
hello
noble
yes
Bol
what
noble
is euglena a unicellular organ
Agio Reply
is euglena a unicellular organism
Agio
how is hydrogen can be heated
Buwembo Reply
what is difference between atom and molecule
Aqeela Reply
Atom is the smallest part of matter; it consists of equal number of protons and electrons. It may have neutrons. A molecule is a compound made of atoms covalently bonded.
Abdelkarim
does amoeba has structure
Mercy Reply
what is the effect of green house on the earth 🌎
kolawole Reply
what is the effect of green house on the earth 🌎
kolawole
what's an atom?
Davy Reply
it's the smallest unit of Matter
Orsine
atom
Eden
smallest part of an element
lydia
also, depending on its (atom's) structure, that is the amount of protons and neutrons and electrons, is the determining factors of what element it is.
Richard
is a smallast particals of an element
Buwembo
it is the smallest part of an element that can take part in a chemical reaction
Ayub
is the smallest part of an element
Jonathan
An atom is the smallest indivisible part of a matter
kpadonu
Oy kl konsa test hay or kitna hay?
Faisal Reply
differences between solid liquid and gaseous state
Ochei Reply
modification of John dalton atomic theory
Ochei
the differences between soliq liquid and gas is that in solid the particle are strongly bonded together by forces of cohesion and the particle are not able to move about but only vibrate in a fixed position but in liquid the particle are loosely bond together and the particle are able to move about
kolawole
2.4g of magnesium reacts with 0.3mol of hydrochloric acid write a balanced chemical equation for the reaction. (b)Determine the limiting reactant
Sheldon Reply
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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