# 18.5 Occurrence, preparation, and compounds of hydrogen

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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:

$\begin{array}{cc}\text{C}\left(s\right)+{\text{H}}_{2}\text{O}\left(g\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.5em}{0ex}}1000\phantom{\rule{0.2em}{0ex}}\text{°C}\phantom{\rule{0.5em}{0ex}}}{\to }& \text{CO}\left(g\right)+{\text{H}}_{2}\left(g\right)\\ & \hfill \text{water gas}\hfill \end{array}$

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:

${\text{C}}_{3}{\text{H}}_{8}\left(g\right)+3{\text{H}}_{2}\text{O}\left(g\right)\phantom{\rule{0.2em}{0ex}}\underset{\phantom{\rule{0.4em}{0ex}}\text{catalyst}\phantom{\rule{0.2em}{0ex}}}{\overset{900\phantom{\rule{0.2em}{0ex}}\text{°C}}{\to }}\phantom{\rule{0.2em}{0ex}}\text{3CO}\left(g\right)+7{\text{H}}_{2}\left(g\right)$

## 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:

${\text{2H}}_{2}\text{O}\left(l\right)+\text{electrical energy}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2H}}_{2}\left(g\right)+{\text{O}}_{2}\left(g\right)$

## 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
covalent bond and ionic bond
so what should we do
Peace
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)
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 )
0.602*10^23=6.02×10^22
galina
Correct 👍... Its 1/10 of the mass number of Al which is 27
Karim
show the steps pls
Faith
correct
Collins
2.7g of Al - 6.02×10^23×2.7/27=0.602×10^23
galina
thanks
Faith
An aqueos solution of sodium hydroxide containing 2g in 200cm3 of solution has a concentration of (NaOH=40).
0.25 mol/dm3
David
0.25M
David
what is the meaning of the term an orbital?
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
Emmanuel
orbitals describe where an electron is likely to be found in an atom. Molecular orbitals perform the same role in molecules
Danny
why is alkynes more reactive than alkenes and alkanes
Alkenes and alkynes are generally more reactive than alkanes due to the electron density available in their pi bonds.
Danny
What are molecules
a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
Danny
True
David
exactly
Harriet
true
lucy
were is ruth
Danny
Perfect
BISWAJIT
what is partial pressure law
what is the structural formular for 2,3-dimethylbutane?
name the following compound (COOH)2
Mercy
CH3-CH(CH3)-CH(CH3)-CH3 this is 2,3-dimethylbutane
galina
(COOH)2 is oxalic acid
thiru
what is chemistry
chemistry is the study of chemical reactions
lucy
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.
Danny
chemistry is the study of matter, it's properties and composition
alexandra
am from Abuja and am in ss1
lucy
ss1 some one translate that for me we use grades in my country
Danny
lucy
okay am a chemistry and biology teacher from Zambia
Danny
should be grade 10 I think
alexandra
thats good Mr mwanza
Harriet
harriet you in grade what
Danny
GCE 12
Harriet
lusaka
Harriet
yes sir
lucy
me ss2
Richard
so are a final year student
kabu
What is the chemical formula for alcohol? is the chemical formula for alcohol?
CH3CH2OH
Anupam
20 element are what element?
What is Chemistry?
studying about chemical reactions
thiru
You are right Vengada
Esther
studying about the rate of chemical is ?
thiru
Chemistry is the branch of sciences dealing with the composition of substances and their properties and reaction.
Jeremiah
chemical reaction is the process in which one or more chemical substances react with other chemical substance and converted one or more different substances.
Aisha
what is isotopy
Isotopy is one of two or more atoms having the same atomic numbers but different mass number.
Esther
is phenomenon where by atom of an element exhibit different mass number but have the same atomic number
lucy
same number of electrons and protons but different number of neutrons
galina
is an atom which has different number of protons but same number of electron such as carbon -12 and corbon 12
Collins
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
galina