Xenon trioxide is an unstable
compound of
xenon
Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
in its +6
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
. It is a very powerful
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
, and liberates oxygen from water slowly, accelerated by exposure to sunlight. It is dangerously explosive upon contact with organic materials. When it detonates, it releases xenon and oxygen gas.
Chemistry
Synthesis of xenon trioxide is by aqueous hydrolysis of :
: + 3 → + 6 HF
The resulting xenon trioxide crystals are a strong oxidising agent and can oxidise most substances that are at all oxidisable. However, it is slow-acting and this reduces its usefulness.
Above 25 °C, xenon trioxide is very prone to violent explosion:
:2 XeO
3 → 2 Xe + 3 O
2 (Δ''H''
f = −403
kJ/
mol)
When it dissolves in water, an acidic solution of
xenic acid is formed:
:XeO
3(aq) + H
2O → H
2XeO
4 H
+ +
This solution is stable at room temperature and lacks the explosive properties of xenon trioxide. It oxidises
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s quantitatively to
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
and
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
.
Alternatively,
15-crown-5 coordinates to xenon trioxide to give a complex stable at room-temperature against mechanical shock.
Alternatively, it dissolves in alkaline solutions to form ''xenates''. The anion is the predominant species in xenate solutions. These are not stable and begin to
disproportionate into
perxenates (+8 oxidation state) and xenon and oxygen gas. Solid perxenates containing have been isolated by reacting with an aqueous solution of hydroxides. Xenon trioxide reacts with inorganic fluorides such as KF, RbF, or CsF to form stable solids of the form .
Physical properties
Hydrolysis of
xenon hexafluoride
Xenon hexafluoride is a noble gas compound with the formula XeF6. It is one of the three binary fluorides of xenon that have been studied experimentally, the other two being XeF2 and XeF4. All of them are exergonic and stable at normal temperatur ...
or
xenon tetrafluoride yields a solution from which colorless XeO
3 crystals can be obtained by evaporation.
The crystals are stable for days in dry air, but readily absorb water from humid air to form a concentrated solution. The crystal structure is
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
with ''a'' = 6.163 Å, ''b'' = 8.115 Å, ''c'' = 5.234 Å, and 4 molecules per unit cell. The density is 4.55 g/cm
3.
Safety
XeO
3 should be handled with great caution. Samples have detonated when undisturbed at room temperature. Dry crystals react explosively with
cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
.
References
External links
Webelements periodic table: page on Xenon(VI) oxide
{{Oxides
Oxides
Xenon(VI) compounds
Inorganic compounds