# 18.5 Occurrence, preparation, and compounds of hydrogen  (Page 2/9)

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$\text{Fe}\left(s\right)+{\text{2H}}_{3}{\text{O}}^{\text{+}}\left(aq\right)+{\text{2Cl}}^{\text{−}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Fe}}^{2+}\left(aq\right)+{\text{2Cl}}^{\text{−}}\left(aq\right)+{\text{H}}_{2}\left(g\right)+{\text{2H}}_{2}\text{O}\left(l\right)$

## Reaction of ionic metal hydrides with water

It is possible to produce hydrogen from the reaction of hydrides of the active metals, which contain the very strongly basic H anion, with water:

${\text{CaH}}_{2}\left(s\right)+{\text{2H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Ca}}^{2+}\left(aq\right)+{\text{2OH}}^{\text{−}}\left(aq\right)+{\text{2H}}_{2}\left(g\right)$

Metal hydrides are expensive but convenient sources of hydrogen, especially where space and weight are important factors. They are important in the inflation of life jackets, life rafts, and military balloons.

## Reactions

Under normal conditions, hydrogen is relatively inactive chemically, but when heated, it enters into many chemical reactions.

Two thirds of the world’s hydrogen production is devoted to the manufacture of ammonia, which is a fertilizer and used in the manufacture of nitric acid. Large quantities of hydrogen are also important in the process of hydrogenation    , discussed in the chapter on organic chemistry.

It is possible to use hydrogen as a nonpolluting fuel. The reaction of hydrogen with oxygen is a very exothermic reaction, releasing 286 kJ of energy per mole of water formed. Hydrogen burns without explosion under controlled conditions. The oxygen-hydrogen torch, because of the high heat of combustion of hydrogen, can achieve temperatures up to 2800 °C. The hot flame of this torch is useful in cutting thick sheets of many metals. Liquid hydrogen is also an important rocket fuel ( [link] ).

An uncombined hydrogen atom consists of a nucleus and one valence electron in the 1 s orbital. The n = 1 valence shell has a capacity for two electrons, and hydrogen can rightfully occupy two locations in the periodic table. It is possible to consider hydrogen a group 1 element because hydrogen can lose an electron to form the cation, H + . It is also possible to consider hydrogen to be a group 17 element because it needs only one electron to fill its valence orbital to form a hydride ion, H , or it can share an electron to form a single, covalent bond. In reality, hydrogen is a unique element that almost deserves its own location in the periodic table.

## Reactions with elements

When heated, hydrogen reacts with the metals of group 1 and with Ca, Sr, and Ba (the more active metals in group 2). The compounds formed are crystalline, ionic hydrides that contain the hydride anion, H , a strong reducing agent and a strong base, which reacts vigorously with water and other acids to form hydrogen gas.

The reactions of hydrogen with nonmetals generally produce acidic hydrogen compounds with hydrogen in the 1+ oxidation state. The reactions become more exothermic and vigorous as the electronegativity of the nonmetal increases. Hydrogen reacts with nitrogen and sulfur only when heated, but it reacts explosively with fluorine (forming HF) and, under some conditions, with chlorine (forming HCl). A mixture of hydrogen and oxygen explodes if ignited. Because of the explosive nature of the reaction, it is necessary to exercise caution when handling hydrogen (or any other combustible gas) to avoid the formation of an explosive mixture in a confined space. Although most hydrides of the nonmetals are acidic, ammonia and phosphine (PH 3 ) are very, very weak acids and generally function as bases. There is a summary of these reactions of hydrogen with the elements in [link] .

can someone please tell me what does an Entropy means
what is chemistry?
what is chemistry
Afiwape
chemistry is a brach of science which deal with the study of the nature, composition structure and with the force that hold the structure together and the change matter will undergo undedifferent conditions
Afiwape
And god has created everything from nothing
Abdelkarim
forms of biotechnology
What is a mole?
pls give me 3 type of transition metal
Copper, Scandium, Vanadium, Iron, Chromium, Cobalt
Jumaane-Kalif
ion zinc hydrogen
Abdul
that is not true
Jumaane-Kalif
stop posting foolishness
Jumaane-Kalif
how do I name compounds
depends on the compound. as you may know there's transition metal compounds and there's organic compounds and so on and so forth.
Jumaane-Kalif
what is electricity
electricity refers to the flow electrons
John
Hi. please can you tell me more on chemical equation
When 1 or 2 chemicals react, they rearrange their atomic composition forming new compounds. The total mass before and after is the same/ constant. Chemical equations of same reactants react in same ratios e.g. 1 Na ion reacts with 1 water molecule or a multipier like 1 mole of Na ions react with 1
Abdelkarim
Mole of water molecules. In that example we multipied by 6.02*10^23 or avogadro constant (L). Or 2 Na+ ions with two water molecules. The arrow means '' to form '' Some times conditions or reactants are written above the arrow like H+ or enzyme or temper, sometimes physical states are written
Abdelkarim
Beside the chemical Aqueous (aq) which means solute dissolved on water. Solid (s) etc Some chemical equations are written next to it ΔH= # which means enthalpy change which describes if the reaction is endothermic (+) or exothermic (-).
Abdelkarim
Some are reversible and have half double arrow sign.
Abdelkarim
what is the meaning of atoma
what is theory
what is chemical compound
Lorrita
A compound is the result of chemical bonding between 2 or more different elements.
Abdelkarim
Why is an atom electrically neutral?
Clara
the same number of electron , proton present in an atom.thats why it is electrically neutral
debibandita
difference between Amine and amide
what is the difference between alkanal and alkanone
difference between alkanol and alkanal
Michael
whaatt
Saturday
you are not well at all
Ibrahim
is organic compounds used for drying agent
Sulfuric acid is used as a drying agent.
Abdelkarim
what is an atom
An atom is the smallest part of an element, for instance gold atoms are the smallest part of gold that can enter a reaction. An atom must consist protons and electrons of equal number. You can think of those subatomic particles as spheres, but not orbiting randomly they move in specific way in
Abdelkarim
That was partially described mathematically. As a muslim, we believe that god created all matter from nothing. He is the Able, and only who can create matter in the begging in the big bang that was described in the Quran in chapter 17 verse 30, 1400 years ago, you can read it from internet.
Abdelkarim
what is electron affinity
John
do you have a private jet
Ibrahim
what is acid
Proton donor (H+). Like in lemons, oranges and some medicines.
Abdelkarim
what is titration? and how can i get my readings?